Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Honored in official journal of a scientific society, scientific journal  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Honored in official journal of a scientific society, scientific journal  Country：Japan

Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Language：Japanese   Publisher：Transportation Research Procedia  

Impact of heavy vehicles on roundabout entry capacity is generally considered through a heavy vehicle adjustment factor fHV which is calculated by heavy vehicle percentage and passenger car equivalent (PCE hereafter) value. The PCE value of trucks is generally set as 2.0 and estimated based on several considerations such as entry capacity and move-up time. All of these considerations are influenced by local driver behavior and geometry conditions. Thus, this paper aims to estimate entry capacity considering the characteristics of heavy vehicle behavior in Japan by microscopic simulation. Then based on the simulation results, the PCE value is also examined. Through the simulation study it is found that entry capacity is reduced when heavy vehicle percentage increases. Moreover, estimated PCE results show that the PCE value of entry flow increases when circulating flow increases but decreases when circulating flow is in high level. Also it is found that PCE of entry flow is lower than that of circulating flow which has priority at roundabouts.

DOI： 10.1016/j.trpro.2016.06.026

Web of Science

Scopus

Language：Japanese   Publisher：Transportation Research Procedia  

This study aims to find out the necessary target travel speeds of roads in functionally hierarchical network which can achieve the target travel times for connecting centers with five different functions, considering the distribution of centers in the subjective area. In this paper, hierarchical road classification scenarios which consists of target travel speeds and road spacings are developed for differentiating road functions. Then travel times under the certain scenario are numerically calculated by an approximate method. Here, the calculation is based on a combination of hypothetical grid network and the actual motorway network. Finally, an application study of Tokaido region in Japan and southwest region in Germany demonstrated the impact of hierarchical road classification scenario on the achievement of the target travel time between centers in different categories.

DOI： 10.1016/j.trpro.2016.06.061

Web of Science

Scopus

Language：Japanese  

DOI： 10.1016/j.sbspro.2014.07.225

Web of Science

Language：Japanese  

DOI： 10.1016/j.sbspro.2014.07.233

Web of Science

Language：Japanese  

DOI： 10.1016/j.sbspro.2012.04.090

Web of Science

Publisher：Transport Policy  

In Japan, the mobility functions of principal arterial roads are hindered by lined-up roadside facilities and densely located signalized intersections. As one of the solutions, it is necessary to consider a functional hierarchy of road networks, based on the structure and traffic operations of each road. The purpose of this study was to propose an index to evaluate the degree to which the road network could be used hierarchically according to their mobility function, based on the location of the bases and the location of roads at each level of the hierarchy, and to propose a method to evaluate the road network using this index. To accomplish this, we proposed a four-level method for the evaluation of the functional hierarchy of road networks based on the derived index values. As a case study, we calculated the degree of hierarchy for the road networks in northern Mie and western Shizuoka. The results showed that the current evaluations of the functional hierarchy in these regions were low, and that introducing mid-level roads was necessary to improve the current situation. The evaluation method proposed in this study will enable us to examine the ideal network configuration for each road in the region to exhibit its mobility function as a preliminary step to studying solutions to various road network issues, such as ensuring the smooth movement between bases and safety. © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the World Conference on Transport Research – WCTR 2023.

DOI： 10.1016/j.tranpol.2024.06.012

Scopus

Publisher：IATSS Research  

Until early 2000s, modern roundabouts (RABs) were poorly understood in Japan and were not fully recognized as a form of at-grade intersections. The RAB research projects of the International Association of Traffic and Safety Sciences (IATSS), which began in 2009, started with examining the applicability of RABs in Japan and have steadily progressed to various stages of field experiments, social implementation, and dissemination promotion activities. These RAB research projects, which lasted for approximately seven years, are considered to have played a significant role in the practical application of RAB in Japan. This paper provides a chronological overview of the history, content, and development status of these projects and records and discusses the role that IATSS research projects played in the early days of RABs in Japan.

DOI： 10.1016/j.iatssr.2024.02.006

Scopus

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

<p>Although the road network in Japan has been almost completed in recent years, travel speeds are said to be on a low level compared to other countries. It is important to compare travel speeds in Japan and abroad when the influence of traffic volume is negligibly small, and to clarify road structures and traffic operations that result in the differences in travel speeds. Recently, it is getting possible to easily grasp travel speeds and road structures around the world through the collection and publication of location information and aerial photographs by Google Maps. The objective of this paper is to compare the off-peak travel speeds in Japan, the U.S., and Germany using Google Maps, and to analyze the factors that contribute to the differences. It was revealed that the travel speeds in Japan are lower than those in the U.S. and Germany, and that the differences in the density of signalized intersections and the speed limit settings are significant factors to them.</p>

DOI： 10.14954/jste.10.2_1

CiNii Research

Publisher：Sustainability (Switzerland)  

Crossing pedestrians may significantly affect the capacity of the left-turn (LT) lane at signalized intersections while sharing the same signal phase in the left-hand traffic system, the quantitative estimation method is still not intensively discussed when considering the vehicle yielding maneuver. Despite the Road Traffic Act in Japan mandating vehicles to yield to pedestrians, instances of vehicles crossing in front of pedestrians are frequent. This study aims to refine the evaluation of LT lane capacity by introducing a novel vehicle yielding maneuver model, considering factors such as pedestrian numbers, crosswalk length, and signal timing. The model, developed using data from various Japanese crosswalks, is subjected to Monte Carlo simulation for validation. Comparative analysis with existing methods in Japanese and U.S. manuals, along with observed data, highlights the effectiveness of our model. This innovative approach has the potential to mitigate vehicle–pedestrian conflicts and reduce air pollution. By incorporating techniques such as signal optimization and two-stage crossing, our model contributes to sustainability while maintaining efficient traffic flow.

DOI： 10.3390/su16062313

Scopus

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

<p>The concept of a functional hierarchical road network is important as one of the solutions to the road traffic problems that still occur in Japan, where the road network has been steadily developed. This study aims to propose a method to evaluate in which degree of functional hierarchy the road network is being used. In a virtual road network with three levels of hierarchy, the shortest routes are searched under the free flow conditions, and the road use characteristic indices are calculated such as trip lengths and use rates of each hierarchical level. Based on the conditions of the road network represented by these index values, a method to evaluate its functional hierarchy in four degrees is proposed. As a case study, the degree of hierarchy was calculated for the road networks in southern Gifu and western Shizuoka. The results revealed that the current evaluations of the functional hierarchy in these areas were low, and that the mid-level roads are required for improving the current situation.</p>

DOI： 10.14954/jste.9.2_a_69

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

<p>The road network in Japan has been steadily developed until today, however, some issues are remaining such as low travel speeds on main roads and through-passing traffics into minor streets in residential areas. This is considered because of insufficient consideration of the hierarchical function of each road at the planning stage. For this reason, it is necessary to reconsider the road network from the functional hierarchy perspective of whether each road is hierarchically being used according to its target function. Therefore, the objective of this study is to clarify influencing factors of the functional hierarchy based on questionnaire surveys for experts in road design and planning. As a result, it was found that road conditions such as the trip length and the travel speed affect the functional hierarchy, and the combination of them is necessary for proper evaluation of the functional hierarchy.</p>

DOI： 10.14954/jste.9.2_a_35

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

DOI： 10.14954/jsteproceeding.43.0_403

CiNii Research

Publisher：Physica A: Statistical Mechanics and its Applications  

The emergence of Autonomous Vehicles (AVs) could provoke unexpected challenges in urban traffic environments. One such crucial challenge is the conflicts between pedestrians and AVs, particularly on unsignalized mid-block crosswalks (UMC), where pedestrians are exposed to the AV flow. This study investigates the efficiency and safety performance of a UMC in the presence of both AVs and pedestrians considering the diversities in their behaviors. Through empirical analyses, two pedestrians’ crossing decision models are built and four groups of speed profiles are classified. Meanwhile, based on previous literature, defensive and competitive driving strategies are assumed for AVs. The simulation is implemented on an agent-based framework that can dynamically reproduce the kinematic interactions between pedestrians and vehicles. Results indicated that with a reasonable safety margin (2.5 s), percentages of low post encroachment time events for competitive AVs with different pedestrian types are smaller than defensive AVs with differences of 0.2% to 2.9%. The average delays of competitive AVs for all pedestrian types are smaller than defensive AVs with a maximum estimated difference of 39 s. Moreover, the analysis showed that lowering the speed limit may reduce the crash rate of competitive AV up to 0%. It is also found that the pedestrians who make reckless crossing decisions and change their speed drastically during the crossing process are more likely to incur crashes with competitive AVs. Therefore, if pedestrian behaviors can be regulated reasonably, competitive AVs with appropriate parameter settings are most suitable for UMC in the future.

DOI： 10.1016/j.physa.2022.128083

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Scopus

Language：English   Publisher：Accident Analysis and Prevention  

Pedestrian distraction may provoke severe difficulties in automated vehicle (AV) control, which may significantly affect the safety performance of AVs, especially at unsignalized mid-block crosswalks (UMCs). However, there is no available motion-planning model for AVs that considers the effect of pedestrian distraction on UMCs. This study aims to explore innovative approaches for safe and reasonable automated driving in response to distracted pedestrians with various speed profiles at UMCs. Based on two common model design concepts, two new models are established for AVs: a rule-based model that solves motion plans through a fixed calculation procedure incorporating several optimization models, and a learning-based model that replaces the deterministic optimization process with policy-gradient reinforcement learning. The developed models were assessed through simulation experiments in which pedestrian speed profiles were defined using empirical data from field surveys. The results reveal that the learning-based model has outstanding safety performance, whereas the rule-based model leads to remarkable safety problems. For distracted pedestrians with significant crossing-speed changes, rule-based AVs lead to a 5.1% probability of serious conflict and a 1.4% crash probability. The learning-based model is oversensitive to risk and always induces high braking rates, which results in unnecessary efficiency loss. To overcome this, a hybrid model based on the learning-based model was developed, which introduces a rule-based acceleration value to regularize the action space of the proposed learning-based model. The results indicate that the hybrid approach outperforms the other two models in preventing crash hazards from distracted pedestrians by employing appropriate braking behaviors. The high safety performance of the hybrid models can be attributed to the spontaneous slowing down of the vehicle that initiates before detecting pedestrians on UMCs. Although such a cautious driving pattern leads to extra delay, the time cost of the hybrid model is acceptable considering the significant improvements in ensuring pedestrian safety.

DOI： 10.1016/j.aap.2022.106711

Web of Science

Scopus

PubMed

Publisher：Transportation Research Part F: Traffic Psychology and Behaviour  

Traffic safety has always been a hot topic for human-driven (HDV) and autonomous vehicles (AV) mixed flow. The conflict between permitted right-turn vehicles (PRT) and opposing through vehicles (TH) at signalized intersections (left-handed traffic) is extraordinarily critical. AVs with aggressive behaviors are able to accept short gap time without losing safety. However, such a turning maneuver may lead to dangerous feelings and cause unexpected reactions of approaching drivers. This study aims to investigate and model drivers’ reactions in TH movements to PRT AVs considering the trust degree of drivers to AVs. Questionnaire surveys and driving simulator experiments were conducted for 41 participants. Results reveal that the right turn timing of PRT AV will significantly influence drivers’ reactions. Basically, TH drivers will brake with a high probability under the situation of small expected post encroachment time (PET). It is also found that female drivers and drivers with low trust in AVs are more vigilant to PRT AVs than other drivers. Based on this finding a two-layer model for reproducing TH drivers’ reactions to PRT AVs is proposed. The first layer is to determine the braking decision and the second layer is to calculate the parameters of braking behaviors (brake lag, braking time, and speed drop). The significance and coefficients variables in these models proved that the trust in AV will influence drivers’ decisions and braking behaviors (brake lag and braking time). The more the drivers trust AVs, the smaller the expected PET to AVs they can accept for passing without braking, and the more gently they will brake (longer brake lag and shorter braking time) due to the cutting in of PRT AVs. This effect will become significant after drivers have experienced several interactions with AVs.

DOI： 10.1016/j.trf.2022.06.018

Web of Science

Scopus

Publisher：Transportation Research Part C: Emerging Technologies  

Merging sections on freeways are typical bottlenecks for traffic efficiency and safety. The connected and automated vehicles (CAV) technology has great capability in improving traffic performance of merging bottlenecks. Current approaches of system optimal cooperative merging control assume single fixed merging point (CMC-SMP) for on-ramp vehicles to reduce the complexity of their models. Non-fixed merging positions have the potential to further improve merging operations but may lead to the computational explosion. To solve this core contradiction, this study proposes a novel hierarchical system optimal cooperative merging control model considering flexible merging positions (CMC-FMP) to realize safe and efficient merging processes. The upper-level – the tactical planning model is formulated as a non-convex mixed integer quadratically constrained programming, aiming at minimal total travel time in the control zone. It optimizes not only the merging sequence but also vehicles’ critical states in merging processes, such as the state of on-ramp vehicles when they merge. The lower-level - the motion planning model generates feasible trajectories and the next step actions for every vehicle. A Monte Carlo Tree Search-based decomposition algorithm (MCTS-DA) is further designed to improve the computational efficiency of the tactical planning model. Meanwhile, solutions of MCTS-DA are proved to have good optimality compared to the direct solving method. A batch-based scheme is developed to realize real-time control. The results reveal that the average delays of CMC-FMP are remarkably lower than those of CMC-SMP. Especially in low on-ramp ratio scenarios, the difference in improvement can reach 64%. Furthermore, the sensitivity analysis indicates that large safe merging margins and short merging sections are disadvantageous for traffic efficiency for the merging flow controlled by CMC-FMP.

DOI： 10.1016/j.trc.2022.103650

Web of Science

Scopus

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

DOI： 10.14954/jste.8.4_b_18

CiNii Research

Language：Japanese   Publisher：International Journal of Intelligent Transportation Systems Research  

Field experiments of autonomous vehicles (AVs) have been conducted in many countries. However, efficiency evaluation of AV mixed flow and safety evaluation of conflicts between AVs and pedestrians in the real-world case are still limited. This study aims at evaluating the efficiency and safety of left-turn (LT) vehicles and pedestrians in signalized intersections, under the condition of AV mixed flow, by developing a simulation model. Post Encroachment Time (PET) and LT capacity were obtained. Further, gap/lag acceptance behavior and reaction time of LT vehicles were found to be critical parameters that affect efficiency and safety evaluations.

DOI： 10.1007/s13177-021-00276-z

Web of Science

Scopus

Publisher：IATSS Research  

Road traffic crashes (RTCs) are influenced by a driver's awareness and attitude toward road safety, as well as the socio-economic status, infrastructure development level, traffic status, social system, and traffic safety culture of the area to which the driver belongs. In this study, based on the results of a questionnaire survey conducted in seven countries, the characteristics of each country concerning tolerance for traffic violations, dangerous driving, and acceptance for road safety measures were studied. It was suggested that a high tolerance for traffic violations and dangerous driving might affect traffic violations and RTCs in each country. Additionally, to reduce the tolerance for traffic violations and dangerous driving, the promotion of road safety education, especially among young and male drivers, and stricter regulations and enforcement were suggested.

DOI： 10.1016/j.iatssr.2021.10.002

Web of Science

Scopus

Publisher：IATSS Research  

Road traffic safety is a crucial global objective. It is important for every country to review and improve road safety policies and strategies, based on an objective understanding of its own road traffic safety situation in the world. With the aim of contributing to such a review and understanding, this study conducted a multi-country survey to gather information about various facts related to legislation, enforcement, and education, which are designed to achieve safer drivers in nine countries, by using a common format. This paper introduces the results of the survey with a particular focus on legislation and enforcement regarding speed limit violations and red-light-running as well as on education within the driving licensing systems. It highlights variations, in terms of penalty settings and enforcement levels, in different countries; it also examines the training durations necessary for acquiring a driving license and license renewal procedures. In this way, it demonstrates the potential and significance of understanding the relative position of each country in terms of road traffic safety through an international comparison despite its limited information.

DOI： 10.1016/j.iatssr.2022.01.004

Web of Science

Scopus

Publisher：IATSS Research  

DOI： 10.1016/j.iatssr.2022.03.005

Web of Science

Scopus

Publisher：IATSS Research  

Traffic violations are recognized as one of the main causes of traffic accidents and have been found to be closely associated with driver attitudes toward traffic safety. In this study, a modified theory of planned behavior (TPB) was used to model the effects of driver safety attitudes on traffic violations, based on a questionnaire survey of 1505 drivers in China. In light of the strong correlations between the observed items, the items of the TPB components were grouped into several parcels, using an item-parceling method. Parcel-based structural equation modeling was then used to operationalize the modified TPB. The results indicate that the proposed model can accurately predict the occurrence of traffic violations based on the observed items related to driver traffic safety attitudes. It was found that driver attitudes, subjective norm, and perceived behavior control significantly affect traffic violations. For predicting traffic violations, driver attitudes toward traffic safety policies had the greatest influence, followed by driver attitudes toward risky driving behaviors and the attitudes of others toward risky driving behaviors. Finally, suggestions on traffic enforcement and education to reduce traffic violations are proposed based on the results.

DOI： 10.1016/j.iatssr.2022.02.001

Web of Science

Scopus

Publisher：IATSS Research  

One of the main pillars for improving road safety in any country is a good understanding of traffic safety culture and the driving behavior of local drivers. The primary aim of this study was to determine whether Egyptian drivers differ in traffic safety attitudes and level of acceptance of risky driving behavior. A questionnaire survey was conducted on the driving cognition of the participants. An exploratory factor analysis was used to assess the number of factors that differentiated the three types of drivers. Then a hierarchical cluster analysis was performed to group the drivers with similar patterns of scores on the factors into clusters. Three driver clusters emerged: The drivers in cluster 1 were “drivers who rigidly followed regulations” (51.7%). The drivers in cluster 2 were “drivers who violated safety precautions” (23.3%). The drivers in cluster 3 were “drivers who had a tendency to violate regulations” (25.0%). A similarity between the social norms and personal attitudes of drivers was found. This can be explained by the high social norm of violating traffic laws, which can lead to more drivers accepting violations. The majority of the older drivers and drivers with no violations or traffic accident on their record in the past 2 years were in cluster 1. Cluster 2 had the highest proportion of young drivers who wore their seat belts and used hands-free phones while driving. Cluster 3 drivers accepted very dangerous violations, such as texting while driving, driving while intoxicated, and driving at very high speeds. They reported significantly more traffic accidents, but no more violations than the other two clusters. The results of this study can be used to improve road safety programs for education and enforcement in Egypt.

DOI： 10.1016/j.iatssr.2021.11.007

Web of Science

Scopus

Publisher：IATSS Research  

While the number of road fatalities is declining in developed countries, it is still increasing globally, especially in middle-and low-income countries. In addition to the driver's individual awareness and attitude toward traffic safety, various factors such as the development of road infrastructure and the legal system may have a significant influence on the occurrence of traffic accidents. Thus, it is essential to consider these factors to enhance traffic safety and achieve Sustainable Development Goal (SDG) Targets of 3.6. In this study, we developed an Elastic Net Regression model to evaluate the factors that influence an individual's traffic violations and accidents based on an international questionnaire on traffic safety attitude, country fact survey data on traffic regulations, and other statistical databases. As a result, it was revealed that: i) In addition to country-level factors, the individual's attributes and attitudes toward traffic safety have an influence on the experience of traffic violations and accidents. and ii) While the same variables regarding individual attributes and attitudes are selected for both traffic violations and accidents, the selected variables relating to country factors differ between violations and accidents.

DOI： 10.1016/j.iatssr.2021.12.004

Web of Science

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

<p>Full signalized traffic circles are operating in some countries to serve the heavy turning traffic flows at large-sized road junctions. Their capacities are influenced by many factors, such as the traffic conditions, signal control types and geometric layouts. The objective of this study is to find out the specified traffic demand conditions that signalized traffic circles are preferred in different cases of the number of lanes and lane configurations. A signal optimization model for the traffic circles is proposed for investigating five cases of signalized traffic circles under various traffic demand conditions. The results showed that signalized traffic circles have higher capacity than signalized intersections in some specific cases, e.g. when the total number of approach lanes reaches five or when more than one right-turn lanes are required. Besides, an analysis on the relationship between the capacity and the occupied area is conducted to further consider the geometric influence.</p>

DOI： 10.11175/easts.14.1958

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

<p>Weaving segments can be one of the crucial road facilities in terms of efficiency and safety on urban expressways. The traffic operation in weaving segment is different from the basic segment due to the crossing of multiple traffic streams. Also, quality of service (QOS) varies among lanes due to different lane utilization rate (LUR). Therefore, this study aims at establishing a lane-based evaluation procedure of QOS through developing LUR estimation models. With the data from two urban expressway sections in Nagoya and Tokyo, Japan, LUR is found to be significantly affected by cross-section flow, merging ratios, diverging ratios, and cross-section position. The model validation reveals that the model can reproduce traffic distribution. Lane-based average speed and density are adopted as measure of effectiveness (MOE), and level of service (LOS) criteria is determined by cluster analysis. Case study shows that the procedure can reflect QOS in each lane at every cross-section.</p>

DOI： 10.11175/easts.14.1870

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

<p>In the road project evaluation, cost-benefit analysis is conducted using the daily speed-flow relationship (Q-V), which is uniformly determined according to the road types and number of lanes. However, the existing Q-Vs cannot accurately reflect actual road traffic conditions, and they did not sufficiently take into account regional traffic conditions. In order to fill these research gaps, in this study, Q-V using traffic flow variations and the hourly speedflow relationship (q-v) considering road structure and traffic operations is modeled. The time average travel speed for each time period is calculated by using the traffic flow variations of the actual observed data and q-v. Then, by taking the weighted harmonic mean of these values, the daily average travel speed of a certain daily traffic volume was calculated and Q-V was set. The shape of the Q-V curve can be explained by the traffic flow variations, and the estimated model made it possible to estimate the Q-V considering the actual road and traffic conditions.</p>

DOI： 10.14954/jste.8.2_a_62

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

DOI： 10.14954/jste.8.2_a_15

CiNii Research

Publisher：Asian Transport Studies  

Conflicts between pedestrians and left-turning vehicles cause pedestrian safety hazards and decrease vehicle turning capacity at signalized intersections. This commonly occurs in Japan where they share the same traffic light phase. Road capacity is influenced by the interaction between them. Autonomous vehicles (AVs) promise to improve the safety and efficiency of road networks. However, they will face the same problems as human-driven vehicles with pedestrian avoidance. Thus, this study estimated the capacity of the left-turn lane, in Japan, under AV mixed flows taking into account AV penetration rates, pedestrian flow rates, and crosswalk length. The impact of AVs on capacity was analyzed with different settings for the critical gap between vehicles and pedestrians. It was found that if AVs comply perfectly with traffic law, the capacity of the left-turn lane sharply decreases, especially in the case of long crosswalks.

DOI： 10.1016/j.eastsj.2022.100070

Scopus

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

DOI： 10.14954/jsteproceeding.42.0_455

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

DOI： 10.14954/jsteproceeding.42.0_463

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>In recent years, the annual number of traffic fatalities in Japan has been in a decreasing trend. In order to further reduce the number of traffic accidents in the future, it is necessary to appropriately understand the relationship between the unsafe driving behaviors such as traffic violations or dangerous driving, and drivers' cognitions on them, which may directly result in traffic accidents, so that effective traffic safety policies and enforcement can be implemented. Therefore, the objective of this study is to quantitatively figure out drivers' cognitions on various unsafe driving behaviors. According to the result of the structural equation modeling based on the questionnaire survey to Japanese drivers, it was found that the younger age group the drivers belong to, the more positive attitudes they would hold for unsafe driving behavior and the more confident in their driving skills. Besides, the difference of influence by age group is particularly significant in drunk driving and careless driving, while less in overspeed driving.</p>

DOI： 10.2208/jscejipm.77.5_i_915

CiNii Research

Language：English   Publisher：Accident Analysis and Prevention  

Visibility can be identified as one of the critical determinants for the safety performance of autonomous vehicles (AVs) on unsignalized mid-block crosswalks (UMC), which may be significantly influenced by build-up environment and surrounding vehicles. This study investigates the safety performance when AVs interact with pedestrians approaching from far-side sidewalks to UMCs considering the visual occlusion of opposing vehicles. A mathematical model is proposed for judging the visibilities of objects from observers’ location under the impact of visual obstacles and is embedded into an agent-based pedestrian-vehicle interaction framework. Two yielding decision modules is assumed for AVs: The normal decision module implements the pedestrian priority rule simply based on the current detectable information, whereas the memory aid decision module extends AVs’ detection abilities by incorporating the memory data. Through simulation experiments, it is found that the percentages of short post encroachment time (%SPET) between AVs and far-side pedestrians reach peaks when the pedestrian flow rate is 300–400 ped/h. When opposing vehicles are in stationary queue conditions, %SPETs are only sensitive to the net distance between the last opposing vehicles in the queue and crosswalks (Dqueue). As the Dqueue decreases to lower than 15 m, %SPETs start to increase drastically. However, when opposing vehicles are in free flow conditions, %SPETs are influenced by multiple factors such as pedestrians’ crossing decisions, sizes and flow rates of opposing vehicles. Furthermore, only when opposing vehicles are in free flow conditions, memory aid AVs can significantly eliminate the impacts of opposite vehicles. Finally, several countermeasures are developed to enhance the visibility and safety at UMCs based on the findings of this study.

DOI： 10.1016/j.aap.2021.106468

Web of Science

Scopus

PubMed

Language：English   Publisher：Accident Analysis and Prevention  

A critical safety problem in road networks is the conflicts on unsignalized crosswalks. Thus, a proactive approach to assess pedestrian safety performance is required. Simulating the microscopic road user behavior in a virtual platform is one of the typical approaches. However, current simulation tools are not flexible enough to properly reproduce various behaviors of pedestrians and drivers considering their interactions with the road environment and other road users. Therefore, the objective of this paper is to propose a novel agent-based framework for evaluating pedestrian safety at unsignalized crosswalks. Unsignalized mid-block crosswalks with refuge islands (UMCR) are considered as an example facility to implement the proposed framework, where relevant behavioral elements such as the reaction time, visual field with obstacles, and minimum safety margin time are addressed. Not only the pedestrian-vehicle interaction is modeled but also the vehicle-vehicle interaction is considered. Empirical validation on a UMCR shows that the proposed framework can reproduce reliable distributions of the post encroachment time compared to the observed distributions within an acceptable error range. The sensitivity analysis reveals that the high reaction time of drivers, small safety margin time, and visual obstacles near crosswalks increase the probability of serious conflicts. The results also show that the framework can reproduce traffic crashes under assumed extreme road conditions.

DOI： 10.1016/j.aap.2021.106288

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.12962/j20861206.v36i1.9100

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Traffic Engineers  

DOI： 10.14954/jste.7.2_b_55

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

DOI： 10.14954/jste.7.2_b_6

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/23249935.2021.1895360

Language：English  

DOI： 10.1016/j.eastsj.2021.100033

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publisher：Japan Society of Civil Engineers  

<p>Crossing pedestrians is one of the critical factors in proper estimation of turning vehicle capacities at signalized intersections. Although individual pedestrian walking speeds and consequent pedestrian platoon maneuver are influenced by traffic signal settings, crosswalk length and bidirectional interactions of pedestrian flows, the existing capacity estimation methods of left-turning vehicles did not consider these impacts. This study aims to propose a method to estimate the expected pedestrian presence-time that pedestrian platoon occupies the conflict-area, considering the characteristics of pedestrian platoon maneuvers. Referring to the existing method to estimate time-dependent pedestrian presence probability distributions, this study re-estimated the parameters of the model using the additional database with higher pedestrian demand conditions. The model revealed that the increase of opposing pedestrian flow significantly reduces spatial variation. This model was applied to calculate expected pedestri</p>

DOI： 10.2208/jscejipm.76.5_i_1485

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>Although the basic road network in Japan is almost completely constructed, a considerable portion of the roads is not functioning reasonably in terms of the expected mobility performance. The quality of service of the traffic flow is unsatisfactory, particularly on arterial highways due to access functions such as the presence of a number of signalized intersections and roadside access. In order to prevent such issues, it is necessary to clearly define the function of each road at the planning and design stage utilizing the concept of a functionally hierarchical road network. Therefore, the objective of this study is to present a method for setting performance targets necessary for each road level to form a functionally hierarchical road network, and clarify the gap between the current traffic conditions and those targets. Assuming one route using an arterial highway and another route using other local streets, the travel speed on each road type and the distance ratio of each route are evaluated. Based on this analysis, the network requirements for the arterial highway route are clarified in terms of the shortest travel time and lowest travel cost. In addition, the gaps between target travel speed and actual travel speed are analyzed using the aforementioned results as a performance target.</p>

DOI： 10.2208/jscejipm.76.5_i_1235

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>The mobility functions on arterial roads have not been fully performed due to presence of roadside access and a number of signalized intersections in Japan. In order to solve this problem, it is necessary to realize a functionally hierarchical road network that promotes the division of functions of roads according to the length of trips by differentiation of road structures and traffic operations. In this study, hypothetical road networks with three road levels were assumed, for clarifying the impact of road and traffic operation conditions on the trip characteristic indices. Then, by using an index combining the trip characteristic indices of each level of roads, requirements of road and traffic operation conditions for the road network to be used hierarchically was investigated. As a result, the requirements were identified for example, the shorter the interchange spacing is, the greater the free speed differentiation between road levels are required.</p>

DOI： 10.2208/jscejipm.76.5_i_1453

CiNii Research

Publishing type：Research paper (scientific journal)   Publisher：IATSS Research  

DOI： 10.1016/j.iatssr.2020.10.001

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Accident Analysis and Prevention  

In the geometric design of roundabouts, safety-oriented approaches are required rather than specification design ones that simply determine the dimensions of the geometric structural elements. We herein propose a risk index (RI) that combines the invisibility probability and the crash impact as a performance measure for evaluating the safety of the geometric designs of roundabouts, and we also describe a method for calculating this index. Invisibility probability represents the probability that an entering vehicle cannot view a vehicle coming from the upstream in a circulatory roadway and crash impact represents the amount of lost kinetic energy at the time of collision corresponds to the impact of the crash. A numerical simulation to model this RI on the basis of various geometric conditions is further presented. It is demonstrated that the invisibility probability is large when the entry angle is small and that the crash impact increases when the deviation angle decreases. The proposed approach is expected to help resolve issues with currently existing roundabouts and improve the design of future roundabouts to enhance their safety performance.

DOI： 10.1016/j.aap.2020.105702

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Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s13369-020-04810-1

Language：Japanese   Publisher：International Association of Traffic and Safety Sciences  

<p>In recent years, although the number of annual fatalities in traffic accidents in Japan is following a downward trend, the rate of decrease is shrinking. In order to reduce the number of traffic accidents more effectively, it is necessary to implement traffic safety measures based on the drivers’ awareness toward traffic safety. To understand traffic safety awareness of different countries and regions, this study conducted a questionnaire survey with drivers in Japan, Italy, and Egypt as a part of the IATSS research project. Although there was undeniably bias in the data samples, the characteristics of drivers’ awareness on traffic safety in each country were identified through comparing and analyzing their tolerance toward traffic violations and dangerous driving behaviors.</p>

DOI： 10.24572/iatssreview.45.1_58

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Safety Research  

Introduction: Heterogeneous driving populations with many different origins are likely to have various sub-cultures that comprise of drivers with shared driver characteristics, most likely with dissimilar traffic safety cultures. An innovative methodology in traffic safety research is introduced which is beneficial for large datasets with multiple variables, making it useful for the multi-variate classification of drivers, driving attitudes and/or (risky) driving behaviours. Method: With the application of multidimensional scaling analysis (MDS), this study explores traffic safety culture in the State of Qatar using a questionnaire and investigates the similarity patterns between the questionnaire items, aiming to classify attitudes towards risky driving behaviours into themes. MDS is subsequently applied to classify drivers within a heterogeneous driving sample into sub-cultures with shared driver characteristics and different risky driving attitudes. Results: Results show that acceptance of speeding is highest among the young Arabic students and acceptance of distraction and drivers’ negligence such as phone use and not wearing a seatbelt is highest among male Arab drivers. Acceptance of extreme risk-taking like intoxicated driving and red-light running is highest among South-Asian business drivers. Conclusion: It is important and practical to understand risky behavioural habits among sub-cultures and thereby focussing on groups of drivers instead of individuals, because groups are easier to approach and drivers within sub-cultures are found to influence each other. By indicating which groups of drivers are most likely to perform specific risky driving themes, it is possible to target these groups and effectively emphasise certain subsets of risky driving behaviours during training or traffic safety education. Practical Applications: This study provides guidance for the improvement of driver education and targeted traffic safety awareness campaigns, intending to make changes to attitudes and habits within specific driver sub-cultures with the aim to improve traffic safety on the longer term.

DOI： 10.1016/j.jsr.2020.02.009

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Scopus

PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Transportation Research Record  

This study estimated composite headway distributions consisting of follower and non-follower headway elements and used the follower percentage obtained as the estimated parameters of those distributions to evaluate the quality of service (QOS) of traffic flow on Japanese intercity expressways under uncongested conditions. Analysis of pulse data obtained by vehicle detectors at multiple points with differing geometric structures showed that follower percentage is influenced by lane traffic volume, vehicle pair, and lane operation. Use of follower percentage also enabled clear and quantitative comparison and evaluation of the QOS of traffic flow for different lane operation formats, which could not be adequately expressed by such conventional macroscopic indices as average speed and traffic density. This indicates that follower percentage is a suitable performance measure for evaluating the QOS of traffic flow.

DOI： 10.1177/0361198120918575

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Arabian Journal for Science and Engineering  

In areas where traffic demand is high and intersections are closely spaced, the drivers’ desire for quick discharge is demotivated by negative downstream conditions, such as long queues and poorly coordinated traffic signals, which may lead to lower saturation flow rate (SFR) for upstream lane groups. However, existing models do not consider this phenomenon. This paper proposes an improved intelligent driver model for reproducing the impacts of downstream traffic conditions on the discharging behavior of vehicles and the estimated SFR. A micro-simulation platform for two closely spaced signalized intersections is built to test the improved car-following model and to simulate the influenced SFR. Results from the sensitivity analysis and the comparison with empirical data show that the developed model could rationally and reliably reproduce the SFR reduction under different downstream conditions. As the queue in the downstream segment becomes longer and the offset becomes larger due to poor coordination, the SFR at the upstream intersection deteriorates. The developed model can be applied in traffic simulations to provide more realistic discharging behavior considering the downstream conditions.

DOI： 10.1007/s13369-020-04411-y

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Transportation Research Record  

Arterials are important transportation facilities, undertaking the two functions of mobility and accessibility. In the urban area, signalized intersections along arterials are usually closely spaced and bear heavy traffic pressure. Capacities of intersections can be reduced by downstream intersections even without having spillback. This effect will be accumulated and amplified back along the traffic direction and may lead to severe congestion in the upstream intersection which can be frequently observed, especially during peak hours. However, existing traffic simulators cannot capture this phenomenon accurately because they ignore the capacity drop before spillback happens. In this study, downstream influence is quantified by a virtual optimal speed (vop). vop is the speed by which the upstream platoon reaches the endpoint of the queue ahead when the last vehicle in the downstream queue just starts. Based on that, two piecewise regression models, for start-up lost time and saturation flow rate, are formulated to estimate the capacity reduction. These regression models are further introduced to improve the modified cell transmission model (CTM). The result of the simulation experiment shows that the proposed CTM model has better performance in simulating traffic flow on signalized arterials than the existing CTM, especially in reproducing the traffic congestion in upstream. The analysis emphasized the importance of considering the downstream influence when simulating the traffic on signalized arterials. Finally, a sensitivity analysis is designed to further reveal the causes of upstream congestion.

DOI： 10.1177/0361198120916477

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Traffic Engineers  

<p>This study assumed that maneuverability such as car-following status illustrates an element related to driver perception, and investigated a performance measure capable of expressing the maneuverability as the quality of service of traffic flow (QOS). Follower percentage is such an index obtained by estimating the composite headway distribution consisting of follower and non-follower headway elements and is used as a performance measure that expresses car-following status. Analysis of pulse data obtained from vehicle detectors at multiple points on intercity expressways with different geometric structures and lane operations showed that follower percentage is influenced by lane traffic volume, vehicle pair, and lane operation. It is clarified that follower percentage can realistically express the behavioral characteristics of small and large vehicles, respectively, and probabilistically capture followers according to the actual traffic phenomenon. Thus, it can be concluded that follower percentage is a suitable index for evaluating the quality of service of traffic flow on intercity expressways under non-congested flow conditions.</p>

DOI： 10.14954/jste.6.2_a_9

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Traffic Engineers  

<p>At the planning stage of road projects, their feasibility is evaluated by the cost-benefit analysis (CBA). In this process, the speed flow relationship (Q-V formula) based on the road type is being used for traffic assignment in Japan. However, in road projects such as grade separation of intersections, if the traffic volume is unchanged through the project, the estimated travel speed is also unchanged, and the effects of the project cannot be properly reflected to the CBA. In this paper, the impact of signalized intersection density on the free speed of the Q-V formula is analyzed by using a traffic simulator. An impact of benefit that is sensitive to the grade separation of intersections by using the calculated free speed is evaluated. As a result, it was confirmed that the free speed of the Q-V formula changes based on the signalized intersection density, the green time ratio and the desired speed. Finally, three benefits of road projects were calculated by a proposed Q-V formula using the free speed based on the signalized intersection density. And the effect of the new formula was clarified by showing the difference in benefits compared to the conventional method.</p>

DOI： 10.14954/jste.6.2_a_198

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Traffic Engineers  

<p>Free speed (FS) is the speed that drivers would adopt if they were not influenced by the presence of other vehicles. This study hypothesises that the difference between the free speed distribution (FSD) and the actual speed distribution (ASD) is indicative of the quality of service (QOS) of traffic flow perceived by drivers. We use raw pulse detector data and the Modified Kaplan-Meier estimation method to derive FSD, which is then modelled based on cross-section geometry. The proposed model of FSD can be easily applied by practitioners without detailed speed and headway data. Additionally, ASD is investigated under various flow conditions, and a model is developed for its estimation based on geometric factors and traffic flow. We then define the Free Speed Index, <i>FSI = AS/FS</i> as an indicator of expressway QOS perception. <i>FSI</i> was found to decrease with an increase in traffic flow, and its potential applications are discussed.</p>

DOI： 10.14954/jste.6.2_a_244

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Transportation Research Procedia  

Signalized intersections are the major causes of delay to vehicular traffic along signalized arterials. Although a lot of research has been conducted about the optimization of the performance of signalized intersections, it is mostly applicable to the operations stage and involves changing signal phasing schemes. However, due to cost of roadways construction and the additional improvements after construction, the assessment of the potential performance of the roadway is very important even at the planning stage so that the plans do not call for some unfavorable design features along the arterial. The lack of performance oriented planning often leads to poor performance, such as very low travel speeds. In this work, we investigate the travel speed along a hypothesized 4-lane signalized arterial, and examine how it changes due to the signalized intersection density, cycle length, mean desired speed, and the function of the intersection. Results showed that cycle lengths up to 120 seconds were sufficient to yield high travel speed. At higher intersection densities, lower travel speeds will be achieved regardless of the mean desired speed. The function of the signalized intersection was also significant, showing the possibility of maintaining the traffic function of an arterial if it were crossed by a lower level road in the hierarchy. The importance of performance evaluation at the planning stage was further emphasized.

DOI： 10.1016/j.trpro.2020.08.106

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IATSS Research  

Professional drivers play a significant role within the traffic system of the State of Qatar. With developing infrastructure, the need for professional drivers is growing. However, knowledge is lacking about their perception of traffic safety. Therefore, this study investigates the personal acceptance of risky driving and suggested traffic laws among this specific group of drivers, in order to create understanding about their likelihood to commit certain risky driving behaviors and their resistance to the implementation of certain traffic laws. The aim of this study is to establish which personal attributes of professional drivers in Qatar could influence a high likelihood to commit risky driving behaviors, estimating which specific groups of professional drivers impose the highest risk to violate certain traffic laws. Results indicate that transportation mode, origin and years of driving experience are all personal attributes that have a significant impact on the professional driver's risk to commit risky driving behaviors and their opposition to the implementation of related traffic laws. Distressing results have been found for the high likelihood to violate speed in school zones and the high risk to be distracted by any type of phone use while driving, suggesting the need to put emphasize on these safety hazards during the training programs of professional drivers at professional driving schools in the State of Qatar.

DOI： 10.1016/j.iatssr.2019.03.004

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese  

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

<p>In recent years, driving support systems have begun to be installed in the real field, and expectations for improvement in safety and efficiency by autonomous vehicles are increasing. However, these expectations are not necessarily realized at the stage of popularization of autonomous vehicles. Particularly, at signalized intersections, because vehicles interact with each other in a complicated manner, efficiency may be affected depending on the setting of the behavior parameters of autonomous vehicles. Thus, this paper analyzes the influence of setting of parameters of autonomous vehicles on capacity of through lanes at signalized intersections by using simulation and model equation, and the capacity is calculated by using simulation result considering parameter settings and mixture ratio. As a result, while it became clear that the cycle length can be shortened by spreading of autonomous vehicles, it is suggested that by inputting discreet setting of the parameters of autonomous vehicles, the efficiency may decrease.</p>

DOI： 10.14954/jste.5.2_a_167

CiNii Research

Publishing type：Research paper (scientific journal)   Publisher：Global Practices on Road Traffic Signal Control: Fixed-Time Control at Isolated Intersections  

DOI： 10.1016/B978-0-12-815302-4.00001-7

Scopus

Language：English   Publisher：Japan Society of Civil Engineers  

<p>Entry capacity is one of the most important indexes to evaluate the roundabout operational performance. Both the geometric elements and vehicle types have an impact on the entry capacity. Passenger Car Equivalent (PCE) for heavy vehicles is utilized for roundabout entry capacity estimation. In the Japanese Roundabout Manual (JRM), PCE is proposed as a constant value. However, it cannot reflect that the capacity of roundabouts varies with different geometric elements and heavy vehicle percentages. Therefore, the objective of this study is to estimate the PCE for heavy vehicles depending on various geometric elements. Entry capacity and PCE were estimated by the entry capacity equation in JRM and traffic simulator VISSIM, respectively. The results revealed that the entry capacity changes with different geometric elements and is significantly related to inscribed circle diameter. It was also concluded that PCE changes with increasing heavy vehicle percentages in the entering and circulating flows.</p>

DOI： 10.2208/jscejipm.75.i_1167

CiNii Research

Language：English   Publisher：Japan Society of Civil Engineers  

<p>Start-up lost time (SLT, hereinafter) is one of the basic parameters for evaluating the capacities of signalized intersections. In the urban area, intersections are closely spaced and traffic demand is high. Drivers’ ambitions for the quick startup are demotivated by negative downstream traffic conditions, for example, limited available storage length, long queue and/or poorly coordinated traffic signals. The performance of upstream intersection is deteriorated including the growth in the SLT. In this paper, the influence of downstream conditions over SLT is analyzed by empirical study. The result indicates that SLTs at subject intersections are mainly influenced by downstream queue length, offset, segment length, and clearing vehicles. Short downstream segment length, long queue, positive offset, and long clearing time will lead to a high SLT value. Regarding this finding, the effect is further investigated by developing a new car-following model. The new model is built by improving the intelligent driver model and calibrated it with empirical data by a genetic algorithm. Through scenario simulation and comparison with empirical data, it is proved that the new model not only can reproduce the SLT increase under different downstream conditions but also have a good fit with real-world data.</p>

DOI： 10.2208/jscejipm.75.i_1121

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> For the geometric design of a roundabout, a safety-oriented approach is required rather than a simple specification dependent design that normatively determines dimensions of the geometric elements. However, such a safety performance index or evaluation methodology has yet to be included in the Japanese guidelines. In this study, we propose a risk index (RI) that combines the mislook probability and crash impact as a performance index for evaluating the safety of roundabout geometric designs; a method to calculate this index is also described. Then, a model equation to calculate the RI from the geometric conditions throughout the numerical simulation is presented. Finally, it is demonstrated that the mislook probability is greater when the entry angle is lower, and the crash impact increases when the deviation angle decreases.</p>

DOI： 10.2208/jscejipm.75.191

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.iatssr.2017.12.001

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tra.2018.08.039

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.trc.2017.11.022

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.trpro.2018.11.013

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.trpro.2018.11.035

Web of Science

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

In this study, stochastic breakdown phenomena on a two-lane section of a Japanese urban expressway are analyzed and modeled. Because the bottleneck of the subject section is supposed to be a complex geometry with an on-ramp, a horizontal curve and an uphill, analysis is conducted not only by cross section but also by lane to understand the characteristics of breakdowns in detail. For such a detailed analysis, applicability and limitation of the detector data with different aggregation intervals are also considered. Through the analysis, it is found that about 40% of breakdowns in the section occur first on the shoulder lane; one of the causes would be higher merging traffic volume. The estimation of breakdown probability shows that the capacity of the median lane is about 300-veh/h greater than that of the shoulder lane. Furthermore, it is found that the discharge flow rate deteriorates as the elapsed time after breakdown increases, especially at the beginning of congestion.

DOI： 10.11175/eastsats.5.64

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

<p>For the safety performance and smooth operation of roundabouts, designing geometric elements that can realize appropriate driving behavior is an important issue, particularly regarding the S-shaped trajectory which is different from ordinary cross intersections. However in Japan, this kind of driving behavior characteristics on roundabouts has not yet been studied enough. In this study, video surveys for driving behavior by using an UAV were carried out at seven roundabouts with different geometric design and the impact of geometric design elements on driving behavior are analyzed. As a result, the entry corner radius and the turning angle which is formed by entry and exit legs are shown as critical factors for the lateral acceleration applied to the vehicle. Moreover, it is shown that oversized entry corner radius and turning angle smaller than 150 degrees could lead to lower lateral acceleration and result in lower speed control effect on straight through vehicles.</p>

DOI： 10.14954/jste.4.1_a_47

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Recently, a lot of knowledge has been accumulated about breakdown phenomena on expressways, their occurrence mechanisms, stochastic nature, and the differences in the pre- and post-breakdown capacities. However, in sections where lane use characteristics have a large effect – such as in lane drop sections, although capacity reduction is known to occur, there are still many unclear points, and more detailed analysis is necessary. Therefore, in this paper, we analyzed the mechanism before and after breakdown in several sections with different usage of the narrowing lane. Breakdown probability curves were estimated based on lane use characteristics, and it was found that the breakdown probability was highest in merging lanes, followed by passing lanes, and was lowest in lane one. This is because in lane one there is little variation in lane usage before breakdown, and left-side overtaking occurs in the merging lane, showing that the influence of lane use characteristics is large.

DOI： 10.2208/jscejipm.74.i_1411

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Since the revision of the Road Traffic Law in 2014, roundabouts have been implemented and planned throughout Japan, and further spread is expected in the future. The geometric design of roundabout is a process of determining combinations of various geometric elements, and it is indispensable to evaluate safety performance for the entire geometry in this process. However, in Japan, concrete methods and indicators for evaluating safety performance have not been considered. Therefore, in this research, overseas design guidelines have reviewed the policies or features of performance evaluation based on “Fastest Path” and “Deflection Angle”. Furthermore, the geometric design of existing roundabouts was evaluated and the applicability to Japan was discussed.

DOI： 10.2208/jscejipm.74.i_1037

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Entry capacity of roundabouts should be confirmed when considering their introduction. However, since there are still few roundabouts in Japan, the impact of roundabout geometry on entry capacity is still unclear. In addition, although the roundabout entry capacity in Japan is calculated based on the gap acceptance theory, the impact of roundabout geometry on the necessary gap parameters has not been clarified. Therefore, in this study the impact of roundabout geometry on entry capacity of roundabouts was analyzed using empirical data from Japan, and an estimation model of the gap parameters using geometry and traffic conditions as explanatory variables was proposed. Based on this, the influence of roundabout geometry on entry capacity was quantitatively clarified.

DOI： 10.2208/jscejipm.74.i_1399

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

<p>In Japan's unsignalized crosswalks on basic road sections, it is hard to say that safety and efficiency of crossing pedestrians are sufficiently ensured. On the other hand, in recent years, attention has been paid to a "two-stage crossing", that is a method in which a crosswalk is split into two stages by using a median island. However, as application examples are still limited in Japan, it is necessary to quantitatively show its effect. In this study, stop-or-go decisions of pedestrians at crosswalks were analyzed considering the impacts of pedestrian crossing time as well as position and speed of approaching vehicles by using observed data. Based on that, the change of the critical gap at the time of applying the two-stage crossing was estimated by formulating a pedestrian gap acceptance model. In addition, the effect of improving efficiency was quantitatively evaluated, by calculating the average delay of crossing pedestrians using this critical gap.</p>

DOI： 10.14954/jste.4.1_a_8

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3141/2659-08

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.trpro.2017.05.176

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.trpro.2017.05.266

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Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Accurate estimation of travel speed along a transport facility is necessary in order to ensure that the facilities meet the required performance. In this paper, the performance of the Highway Capacity Manual travel speed model is checked for Japanese roads. Then, a travel speed estimation model is developed from data collected along a road section in Hamamatsu City, Japan. The model provides an estimate of the average travel speed along a road section by inputting demand flow rates, section length, number of signalised intersections, signalised intersection density, and the number of access points along the road in the travel direction. It is found that the travel speed slightly increases with increased section length, and decreases with increased access points and higher number and density of signalised intersections.

DOI： 10.11175/easts.12.1604

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Critical gap is an important parameter for not only entry capacity estimation but also safety evaluation at roundabouts. This paper gives an overview on the existing procedures for estimating critical gaps and compares them by applying into an empirical data observed at a roundabout in Japan. Application of other procedures than Raff's method, which has been commonly used in Japan, enables to estimate not only a single representative value of critical gaps (e.g., mean or median) but also their distribution. Through a comparison, differences of the estimated critical gap distributions are presented and discussed considering the limitation in the observed samples.

DOI： 10.2208/jscejipm.73.i_1243

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

One of the measures to inhibit conflicts between pedestrian and left-turning vehicle at crosswalk of signalized intersections is, to provide separate phases for pedestrian and turning vehicle, such as exclusive pedestrian phase or Leading Pedestrian Interval (LPI). LPI is the phase which pedestrian green is displayed a few seconds ahead of vehicle green phase, and in this preceding time interval, a part of pedestrians can be protected from the conflicting left-turning vehicles. From the viewpoint of safety and mobility performance, LPI can be positioned between the conventional four-phase type in which the concurrent pedestrians and vehicles share the same signal phase and the exclusive pedestrian phase type. However, the safety and mobility performance of these three types of signal phasing is unclear. Thus, this study investigates and compares delays of pedestrian and vehicle, degree of saturation, capacity and pedestrian exposure time under those three types of signal phase types. Then an application range of LPI and the boundary condition of exclusive pedestrian phase are discussed.

DOI： 10.14954/jste.3.5_11

CiNii Research

CiNii Research

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Inside intersection pavement markings category in Japan and Philippines are different, and the difference of its impact to mobility performance are still unknown. Left-turn lanes (right-turn in Japan) is one of key movements in urban signalized intersections and their capacity must be maximized. This paper aims to investigate the difference of the mobility performance of the right-turn guide lines in Japan and Yellow-Box pavement markings in the Philippines in terms of saturation flow rate, trajectory variation and speed. The analysis reveals that the turn guide lines are effective in achieving small turning vehicle trajectory variation and high saturation flow rate which are affected by the traffic signal phasing and the geometric layout of the turn lanes of the signalized intersection. The absence of guide lines of yellow box pavement markings creates cross-maneuvering behavior that lower the saturation flow rate of the turning lane.

DOI： 10.11175/easts.12.1637

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

This study aims to identify influencing factors of traffic accidents on Japanese major roads through factor analysis and regression analysis for each accident type, considering their characteristics as rare events. The database consists of a five-year accident record and relevant road traffic condition data on major road sections in Aichi Prefecture, which includes the third largest conurbation area of Japan. From the results of the factor analysis, a trend of high accident rates in broad urban arterials is confirmed, and rear-end or side collisions are widely distributed in suburban areas. From the regression analysis, results reveal that the degree of impact by traffic volume is dependent on accident type, and suggests that several factors related to visibility have an influence on turning and side collisions. The study suggests that improving the quality of traffic flow on major roads by ensuring proper intersection spacing is important for establishing a safer road network.

DOI： 10.11175/eastsats.4.392

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Besides circulating flow, pedestrian flow is another key conflict stream that significantly influences roundabout entry capacity. Due to limited space in Japan, several standard designs such as a physical splitter island cannot always be installed at the roundabout entry/exit. The impact of several influencing factors on entry capacity such as splitter islands was examined by applying a microscopic simulation to our previous research. A regression model was proposed based on the simulation results, which assumed that vehicles yielded to all pedestrians at the beginning of the crosswalk. In this paper, the regression model was validated using field data observed in Japan. The regression model was improved by adding a parameter to reflect drivers’ compliance with pedestrians. The validation results indicate that the improved model shows good fitness to the field data and the results imply that roundabout geometry and traffic flow composition significantly influence entry capacity.

DOI： 10.11175/eastsats.4.350

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

As implementation of roundabouts is being discussed at more numbers of places after the partial revision of Road Traffic Law in 2014, quantifying the impact of heavy vehicles on entry capacity is an important and urgent task in Japan. The objective of this study is to estimate passenger car equivalent (PCE) of heavy vehicles at roundabouts in Japan. Since the number of actual roundabouts is still limited, this study adopts a microscopic traffic simulator for obtaining entry capacity under various heavy vehicle percentages in either entry or circulating flow. Then, passenger car equivalents at entry and circulatory roadway are derived based on the simulated capacities. As a result, it is found that the estimated passenger car equivalent is higher at entry than at circulatory roadway. At the end, entry capacity with heavy vehicles in both entry and circulating flows simultaneously is reasonably calculated by using the estimated passenger car equivalents.

DOI： 10.14954/jste.2.6_11

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

In Japan, reorganization of road network into functionally hierarchical form becomes more important so as to efficiently improve travel performance between centers where daily-life and/or urban services are provided. This study aims at investigating the appropriate composition of a functionally hierarchical road network which can achieve the target travel times set for various connections of centers in the subjective region. Here, composition is defined as a combination of the number of hierarchical road levels, target travel speed, road spacing and access spacing of each road level. In this paper, alternatives of such a composition are derived by considering the impact of road crossings as well as roadside access. At the end, a case study is conducted in Tokaido region, Japan, and travel performance indices, namely travel time and average travel speed, between various types of centers are estimated under each alternative composition of a functionally hierarchical road network. The result shows that road level with higher travel speed (i.e., 50~60km/h) can significantly work especially for the communities in peninsula and mountainous rural area by enhancing the accessibility to urban centers.

DOI： 10.2208/jscejipm.72.i_939

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

The gap acceptance behavior to the opposing through traffic of “permitted” right-turn vehicles is one of the important events for evaluating the safety of signalized intersections. In this study, a decision-making process of gap acceptance was carefully investigated through paying attention to a difference by the number of opposing approach lanes. Moreover, a gap acceptance model of permitted right-turn vehicles at the multilane signalized intersection was developed considering arriving vehicles’ positions in the multiple opposing approach lanes by using binomial logit model. The model estimation result quantitatively showed that the gap acceptance decision is being influenced not only by gap times and arrival through vehicle speeds but also by their driving positions at the intersection approach lane. Furthermore, the calculation result of the critical gap time suggested that it varies depending on the positions of opposing through vehicles in the multilane intersection comparing to the case of single opposing lane intersection.

DOI： 10.14954/jste.2.2_a_85

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

Timing of pedestrian phase plays an important role in the safety and mobility performance at signalized intersections. In order to evaluate the performance, it is useful to understand effects of crosswalk length and signal timing on pedestrian presence position and timing. This study investigates the effects of elapsed pedestrian green time, waiting time, crosswalk length and pedestrian volume on the spatiotemporal probability of pedestrian presence and models its distributions considering these influencing factors. It was found that pedestrian presence probability distributions shift to the moving direction as pedestrians proceed. The shorter pedestrian waiting time and longer crosswalk length lead to the wider distribution of pedestrian presence probability. In addition, application of the pedestrian presence probability model for setting Leading Pedestrian Interval (LPI) is discussed. Possible ranges of LPI are investigated dependent on crosswalk length, vehicle flow rate and ratio of pedestrian having passed the conflict area according to pedestrian directional rate.

DOI： 10.14954/jste.2.2_a_183

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

 More than half of traffic accidents on arterial road networks occur at intersections. To enhance traffic safety, it is essential to identify the risk factors with qualitative manner, and to reform the configuration of intersections and improve the traffic management for removing the risk factors. In this study, first we collected the data of intersection geometric attributes and lane configurations by using virtual database (cf. Google Earth and Google Street View), which was integrated with the data of traffic accidents, road networks, and traffic volume. Then, Poisson regression models were applied to statistically identify the risk factors on categorized traffic accidents. Finally, the expected number of reduction of traffic accidents are estimated based on the regression models when the reformations are applied to the intersections in Kagawa. As a result, those findings are obtained; (i) the geometric attributes of intersections are significantly varied among prefectures (Kagawa, Shiga, and Aichi), which can be considered as regional characteristics; (ii) as the size of intersections becomes large, the risk of traffic accidents becomes worse, which implies that downsizing of intersection may contribute to improve the traffic safety; (iii) according to the proposed reforming scenario for intersections in Kagawa, there is a potential that the total number of traffic accidents could be reduced by more than 35%.

DOI： 10.2208/jscejipm.72.368

CiNii Research

CiNii Research

Language：Japanese   Publisher：IEEE Transactions on Intelligent Transportation Systems  

Pedestrian-vehicle conflicts are considered one of the most common safety problems at signalized intersections. In Japan, the pedestrian flashing green (PFG) is considered a safe time interval for pedestrians at crosswalks to finish crossing before conflicting vehicle streams are released. In most common phasing schemes, pedestrians have the right-of-way along with left-turning vehicles (in left-hand traffic). By law, pedestrians should not enter a crosswalk during the PFG. However, many of them rush into crosswalks without necessarily heeding approaching turning vehicles, which could increase the probability of severe conflicts. The objective of this paper is to analyze and model the probabilistic behavior of pedestrians after the onset of the PFG, which contains the pedestrians' decision of whether to give up crossing, as well as the pedestrian speed distribution. Empirical data analysis showed that longer crosswalks lead to significantly higher pedestrian stop probabilities. Furthermore, there is a significant difference between the pedestrians' speeds in the first and second halves of crosswalks. The results of a Monte Carlo simulation showed that the estimated models closely represent the overall stochastic behavior of the pedestrians from the onset of the PFG until the completion of crossing.

DOI： 10.1109/TITS.2014.2346154

Web of Science

Scopus

Language：Japanese   Publisher：Transportation Research Record  

At roundabouts, the main streams that conflict with entry flow and have a significant effect on entry capacity are circulating flow and pedestrian flow. Pedestrian impact is estimated with an adjustment factor ( fped) in existing methods that were developed under standard roundabout designs, such as a physical splitter island at entry and exit. However, available space may limit these geometric designs in some locations (e.g., in Japan), and, as a result, the impact of driver and pedestrian behaviors on entry capacity probably changes. In a microscopic approach, entry vehicles cross pedestrian flow through available pedestrian gaps. Therefore, gap acceptance behavior is used to reproduce conflict with pedestrians. This analysis aimed to estimate roundabout entry capacity that considers conflict with pedestrians by gap acceptance behavior as well as several influencing factors, including presence or absence of a physical splitter island and the farside pedestrian yield rate (i.e., number of drivers yielding to the total farside pedestrian demand). Entry capacity was estimated two ways, with simulation analysis and a theoretical model. The estimated entry capacity results from the two approaches were compared, and the limitations of each approach were interpreted. Results from the two proposed approaches also were compared with those from the existing fped model that was applied in Highway Capacity Manual 2010 (referred to as HCM fped). Findings imply that HCM fped is not appropriate for Japanese situations. Both proposed approaches are expected to be used in the planning and design stages for roundabout implementation not only in Japan but also in other countries that must consider space limitations and pedestrians.

DOI： 10.3141/2517-07

Web of Science

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Quantifying effects of crosswalk length and signal timing on pedestrians' presence position and timing is an important requirement for evaluating the probability of conflict. It can be utilized to provide a rational safety assessment and improve existing operational policies at signalized intersections. This study investigates the effects of crosswalk length and pedestrian green time on the spatiotemporal probability of pedestrian presence. It was found that the longer pedestrian green time and crosswalk length leads to the wider distribution of pedestrian presence probability. In addition, a surrogate safety measure for assessing pedestrian safety is proposed by utilizing the pedestrian presence probability model.

DOI： 10.11175/easts.11.1403

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

In recent years, field operational tests and implementation of roundabout are actively promoted at several places in Japan, and roundabout has been legally positioned through the amendment of the Road Traffic Act in June 2013. Entry capacity is one of the most important indices for performance evaluation related to the application of roundabouts. However, a criterion of entry capacity including impacts of pedestrians and cyclists based on the observation has not been available in Japan due to the limited observation examples. This paper aims to analyze characteristics of roundabout entry traffic flows based on the field data observed at several existing and/or experimental roundabouts. Entry capacity observed at Roppontsuji roundabout in Karuizawa Town is also examined and compared with the estimated values by a proposed entry capacity estimation model.

DOI： 10.2208/jscejipm.71.i_1017

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

The objective of this study is to clarify a relationship between the road traffic conditions and accident frequency through statistical model analysis towards implementing effective safety measures. A rich accident database was combined with relevant road traffic information by using GIS software, and two different models, i.e. negative binomial regression and multiple regression models were independently applied for estimating accident frequency. As a result, it was found that accident frequency is closely related to average travel speeds and distance between intersections in arterial roads. Regarding non-arterial roads, the result specified different influencing factors by accident type. Furthermore, it suggested a high potential of frequent accident occurrence in non-arterial roads particularly at positions close to the arterial roads with low average travel speed. Finally, the necessity of improving quality of traffic flow and hierarchical road network for road safety was discussed.

DOI： 10.2208/jscejipm.71.i_889

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

For functionally hierarchical road planning, it is important to set the appropriate target network defined by the number of road levels, road spacing and target travel speed of each road level, considering distribution of urban city centers, target travel time among them and demand characteristics. This study proposes a methodology to determine the variables that define target network based on the percentage of urban centers between which their target travel time is achieved as well as construction cost. In this methodology, target travel speed ratio is assumed to be proportional to road spacing ratio between two connected road levels, and the road levels with the highest or lowest target travel speed needs to be given in advance. These assumptions enable to limit the number of scenarios with realistic combinations of road spacing and target travel speed under the trade-off between mobility and access functions. Finally, a simple case study is conducted with a hypothetical grid network assuming some typical urban center distribution. As a result, the effects of number of road levels and target travel speeds on travel time by trip length and construction cost are demonstrated.

DOI： 10.14954/jste.1.2_a_107

CiNii Research

Language：Japanese   Publisher：Japan Society of Traffic Engineers  

The existing methodology for roundabout entry capacity estimation is assuming the standard geometric layout and user behavior in other countries. However in Japan, it is often likely that the physical splitter islands are not implemented mainly due to space limitations, and thus pedestrian behavior and its impacts on entry capacity are different from those in the other countries. In this paper, simulation analyses were carried out with respect to impacts of geometry and user behavior conditions that are typical in Japan on entry capacity, and by using their results a multiple regression model for entry capacity estimation was developed. The model was validated with data observed at Roppontsuji roundabout in Karuizawa, Nagano. It was found that the estimation performance of the proposed model was very satisfactory while the existing methodology overestimates the capacity.

DOI： 10.14954/jste.1.5_19

CiNii Research

Language：Japanese   Publisher：Transportation Research Part C: Emerging Technologies  

Limited pedestrian behavior models shed light on the case at signalized crosswalk, where pedestrian behavior is characterized by group or individual evasion with surrounding pedestrians, collision avoidance with conflicting vehicles, and response to signal control and crosswalk boundary. This study fills this gap by developing a microscopic simulation model for pedestrian behavior analysis at signalized intersection. The social force theory has been employed and adjusted for this purpose. The parameters, including measurable and non-measurable ones, are either directly estimated based on observed dataset or indirectly derived by maximum likelihood estimation. Last, the model performance was confirmed in light of individual trajectory comparison between estimation and observation, passing position distribution at several cross-sections, collision avoidance behavior with conflicting vehicles, and lane-formation phenomenon. The simulation results also concluded that the model enables to visually represent pedestrian crossing behavior as in the real world. © 2014 Elsevier Ltd.

DOI： 10.1016/j.trc.2014.01.007

Web of Science

Scopus

Language：Japanese   Publisher：Transportation Research Record  

Entry capacity is one of the most important indexes for performance evaluation of roundabouts. In addition to circulating vehicles, pedestrian flow is another key conflicting stream that has a significant impact on entry capacity. Pedestrian impact is considered by an adjustment factor in the Highway Capacity Manual 2010. However, this method is limited in estimating pedestrian impact by several influencing factors [e.g., pedestrian approaching side, farside pedestrian recognition rate (FPRR) of drivers, and physical splitter island] that are considered to be significant for representing the characteristics of the Japanese situation. The impacts of these influencing factors are examined by microscopic simulation in this study. Results from the simulation study showed that under the condition without a physical splitter island, entry capacity was reduced more significantly when more pedestrians were from the farside of the crosswalk, whereas capacity relatively increased with decreasing FPRR. Moreover, entry capacity was also increased after the installation of a physical splitter Island. The significance and the necessity of a physical splitter island were demonstrated in this analysis for roundabout design and operation in Japan. This research also showed that those influencing factors (i.e., pedestrian approaching side, FPRR, and physical splitter island) should be coasidered in entry capacity estimation.

DOI： 10.3141/2461-14

Web of Science

Scopus

Language：Japanese   Publisher：Japan Society of Civil Engineers  

It is of great importance to analyze right-turning behavior at signalized intersection given high accident records related to right-turn vehicles, which also helps provide valuable insights into safety assessment of signalized intersection. This study aims to analyze the right-turn vehicle behavior in protected right-turn phase by considering the influencing factors of geometric characteristics and signal operation. It was found based on empirical modeling results that the right-turn vehicle behavior is closely related to geometric characteristics such as intersection angle and setback distance of stop bar. Furthermore, in order to make a balance of both positive and negative impact, the potential strategies may bring upon safety performance of signalized intersection, all the influencing factors related to right-turn behavior were summarized and evaluated. Finally, the necessity of employing microscopic simulation to enable a comprehensive evaluation of surrogate safety meausure (SSM) at signalized intersection was examined.

DOI： 10.2208/jscejipm.70.i_1013

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Quantifying the effects of crosswalk length and signal timing on pedestrian walking speed is an important requirement for providing a rational safety assessment at signalized intersections. This study investigates the effects of pedestrian green time (PG), crosswalk length and pedestrian crossing direction on pedestrian walking speed at signalized crosswalk. It is assumed that the pedestrian walking speeds consist of two components v1 and v2 at two consecutive halves of crosswalk. Empirical analysis shows that the longer crosswalk tends to induce the higher walking speed. Pedestrian walking speed increases as PG proceeds. Furthermore, a comparison of pedestrian speed models for PG and PF (pedestrian flashing green time) demonstrates that pedestrian walking speeds at PF are higher and more variable than at PG. The sensitivity analysis helps understand how these models behave depending on change of each variable.

DOI： 10.2208/jscejipm.70.i_1031

CiNii Research

CiNii Research

Publisher：Advances in Transportation Studies  

Pedestrian safety improvement at signalized intersections remains a critical issue. The major threat comes from frequent interaction with turning vehicles, especially left-turners (left-hand traffic system). This study gains insights into how surrogate safety measure (SSM) can be utilized for pedestrian versus left-turning vehicle conflict assessment, and although a small step, how to relate SSM to limited crash records for crash risk estimation. Based on the video data collected at several crosswalks in Nagoya City, Japan, SSMs, i.e., Post Encroachment Time (PET) and vehicle passing speed at conflict point were extracted for analysis. PETs were estimated for both near-side and far-side approaching pedestrians by identifying the potential conflict points and considering the physical size of left-turning vehicles. The effectiveness of SSMs to reflect the impact of site-specific geometric characteristics and operational conditions upon conflict risk has been demonstrated. Furthermore, crash risk estimation models were developed by using Poisson regression methods based on mean PET, the number of short PETs per hour and average vehicle passing speed at conflict point at each crosswalk. It demonstrates that high turning speed, in conjunction with higher frequency of short PETs result in higher crash rates.

DOI： 10.4399/97888548735445

Scopus

Publisher：Journal of Modern Transportation  

This study aims at identifying crash-influencing factors by facility type of Nagoya Urban Expressway, considering the interaction of geometry, traffic flow, and ambient conditions. Crash rate (CR) model is firstly developed separately at four facility types: basic, merge, and diverge segments and sharp curve. Traffic flows are thereby categorized, and based on the traffic categories, the significances of factors affecting crashes are analyzed by principal component analysis. The results reveal that, the CR at merge segment is significantly higher than those at basic and diverge segments in uncongested flow, while the value is not significantly different at the three facility types in congested flow. In both un-and congested flows, sharp curve has the worst safety performance in view of its highest CR. Regarding influencing factors, geometric design and traffic flow are most significant in un-and congested flows, respectively. As mainline flow increases, the effect of merging ratio affecting crash is on the rise at basic and merge segments as opposed to the decreasing significance of diverging ratio at diverge segment. Meanwhile, longer acceleration and deceleration lanes are adverse to safety in uncongested flow, while shorter acceleration and deceleration lanes are adverse in congested flow. Due to its special geometric design, crashes at sharp curve are highly associated with the large centrifugal force and heavy restricted visibility. © The Author(s) 2013.

DOI： 10.1007/s40534-013-0024-9

Scopus

Language：Japanese   Publisher：Transportation Research Part C: Emerging Technologies  

Analytical evaluation techniques for the safety performance of signalized intersections are applicable to limited scenarios and conditions, whereas simulation-based analysis tools are very flexible and promising. This study is part of intensive efforts to develop a microscopic simulation model for the safety assessment of signalized intersections. One important aspect of analyzing driver maneuver is vehicle paths. Broadly varying paths may result in widely distributed potential conflict points with other movements, which may affect the occurrence probability of severe conflicts. Therefore, this study aims to develop a technique to reproduce the variations in the paths of turning vehicles, considering intersection geometry, vehicle type, and speed. Several signalized intersections in Nagoya City, Japan, with various traffic and geometric characteristics were videotaped. The analysis revealed that the paths of right-turning vehicles (left-hand traffic) are more sensitive to the vehicle speed and turning angle whereas those of left-turning vehicles are more sensitive to the intersection corner radius, turning angle, and vehicle speed. For modeling individual vehicle paths, this study applies the Euler-spiral-based approximation methodology where each trajectory is fitted by an entering Euler spiral curve followed by a circular curve and an exit Euler spiral curve. The proposed models are unique since they provide a realistic and rational representation of the variations in turning vehicles' paths inside intersections. © 2012 Elsevier Ltd.

DOI： 10.1016/j.trc.2012.09.006

Web of Science

Scopus

Language：Japanese   Publisher：Accident Analysis and Prevention  

Pedestrian-vehicle conflicts are considered as a common safety problem at signalized intersections. The threat to pedestrian safety is mainly related to the interaction with turning vehicles, especially left-turners (left-hand traffic system). This study aims to analyze the lag/gap acceptance behavior of left-turners considering pedestrian movement at signalized crosswalks. Furthermore, the severity of pedestrian-vehicle conflicts is addressed by analyzing vehicle speeds at the conflict points. User behavior at several signalized intersections in Japan is observed by using video cameras. It is assumed that pedestrian movements have their origin at either the near-side (the side of the exiting vehicular traffic) or far-side of the crosswalk. Accepted/rejected lags and gaps are extracted, classified depending on the direction of pedestrian movement, and modeled by using Cumulative Weibull distribution function. The results show that drivers tend to accept shorter lags/gaps between near-side pedestrians compared to far side pedestrians. Furthermore, drivers tend to accept short lags while being conservative about short gaps. Simultaneously vehicles clear the conflict area with significantly higher speeds when accepting lags with single pedestrians. This indicates that the conflicts that occur at low pedestrian demand levels are more severe compared to those at high demand levels. © 2012 Elsevier Ltd.

DOI： 10.1016/j.aap.2012.04.006

Web of Science

Scopus

PubMed

Language：Japanese   Publisher：Transportation Research Record  

When the breakdown probability on expressways is being modeled, the identification of breakdowns is a decisive issue. To date, most identification methods have treated all lanes of the main line as one unit; these methods have been conducted mainly by checking the aggregated data of the cross section. However, this cross section-based method oversimplifies breakdown identification for expressway facilities, such as diverge sections, on which preferences for lane usage differ significantly. Therefore, a lane-based method is proposed to identify breakdowns in each lane; the timing of the breakdown is determined by a critical speed, which is optimized by obtaining the most significant speed reductions that accompany the breakdown. The proposed lane-based method is applied to four bottlenecks at diverge sections on intercity expressways in Japan. The superiorities of the lane-based method are as follows. First, the method can identify and exclude semicongested cases, in which some lanes are congested and others are not. At a diverge section of the Toyota junction in Japan, 15 semicongested cases were identified by the lane-based method from the 198 breakdowns identified by the cross section-based method. Second, the timing of a breakdown can be appropriately determined, as it was for 34 cases on this diverge section. These superiorities significantly improve the accuracy of extracted breakdown flow rates, which are underestimated by the existing cross section-based method. The breakdown probability is modeled with the lane-based method on the extracted breakdown flow rates, and the impacts of traffic condition characteristics are discussed. The diverge rate and the lane utilization rate are found to have significant impacts on the breakdown probability at diverge sections.

DOI： 10.3141/2395-10

Web of Science

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

This study aims at developing a crash risk estimation model (CREM) considering the interaction of geometry, traffic flow and ambient conditions for basic segments of Nagoya Urban Expressway. A matched case-control study is firstly designed separately for three traffic conditions; low-density, high-density uncongested and congested regimes. Based on these case-control samples, conditional logistic regression is then applied and the CREM is finally developed. The results reveal that the model has statistical significance and acceptable goodness-of-fit, with 86.6%, 80.5% and 70.2% of predictive performance for each of the three traffic conditions, respectively. Regarding crash influencing factors, with the increase of traffic density, the significance of horizontal geometry affecting crash becomes lower. In contrast, the contribution of vertical geometry to crash risk is on the rise. Meanwhile, the effect of average speed on crashes gets more significant. Besides, nighttime or holiday can increase the relative risk compared to daytime or weekday, respectively.

DOI： 10.11175/easts.10.1916

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

This paper proposes an approach to model the gap choice behavior of merging vehicles under various traffic flow conditions at urban expressway merging sections in Nagoya, Japan. The gap choice is classified into three patterns denoted direct, yield and chase merging. Empirical analysis shows that mainline traffic conditions significantly affect the proportion of gap choice. In addition, yield and chase choices result in further merging position compared to direct one. This fact is necessary to be considered in order to design the acceleration lane to meet driver behavior under relevant operational traffic flow conditions. TTC is adopted as an index to determine the threshold of choosing a merging pattern. The results show that the thresholds of choosing direct/yield or chase, continue to chase or not and direct or yield are 4.3, 3.2 and 5.4 seconds, respectively. The gap choice behavior is modeled by applying binary logit model. The results reveal that relative speed and space gap, traffic conditions, acceleration lane length, and remaining distance significantly affect the gap choice behavior of merging drivers.

DOI： 10.2208/jscejipm.69.i_881

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Existing signal control strategies do not consider pedestrian flows in optimizing signal parameters, which may impose significant delays on pedestrians. This study aims to investigate the rationality and effectiveness of designing signal coordination for pedestrians. A numerical case study in Japan is analyzed. Field survey is conducted to collect the geometric characteristics, signal timings and vehicular traffic condition information. In a parallel approach, the performances of signal coordination for vehicular and pedestrian traffic are estimated by using the vehicular traffic simulation tool Synchro/SimTraffic and the pedestrian simulation tool NOMAD. The results showed that the coordination for the major pedestrian flow led to a significant reduction in average delay (15%). Generally, it is concluded that the effectiveness of pedestrian signal coordination is not guaranteed but depends on the relationship between pedestrian platoon dispersion and the signal cycle length.

DOI： 10.11175/eastsats.2.223

CiNii Research

Publisher：IATSS Research  

Improving pedestrian safety at intersections remains a critical issue. Although several types of safety countermeasures, such as reforming intersection layouts, have been implemented, methods have not yet been established to quantitatively evaluate the effects of these countermeasures before installation. One of the main issues in pedestrian safety is conflicts with turning vehicles. This study aims to develop an integrated model to represent the variations in the maneuvers of left-turners (left-hand traffic) at signalized intersections that dynamically considers the vehicle reaction to intersection geometry and crossing pedestrians. The proposed method consists of four empirically developed stochastic sub-models, including a path model, free-flow speed profile model, lag/gap acceptance model, and stopping/clearing speed profile model. Since safety assessment is the main objective driving the development of the proposed model, this study uses post-encroachment time (PET) and vehicle speed at the crosswalk as validation parameters. Preliminary validation results obtained by Monte Carlo simulation show that the proposed integrated model can realistically represent the variations in vehicle maneuvers as well as the distribution of PET and vehicle speeds at the crosswalk. © 2012 International Association of Traffic and Safety Sciences.

DOI： 10.1016/j.iatssr.2012.03.002

Scopus

Language：Japanese   Publisher：Transportation Research Record  

Because of traffic accidents at signalized intersections, improvement in the design of geometric layouts and operations of intersections is needed. Traffic simulation provides an innovative approach to assessing the safety performance of various layouts and operational policies of signalized intersections. A microscopic simulation model was developed to assess the safety of signalized intersections. The proposed simulation model integrates many key behavioral models of road users, such as the stop-go decision at the onset of a yellow light, turning paths, turning speeds, start-up response time, and pedestrian gap acceptance models. The main feature of these empirical models is their consideration of the stochastic behavior of road users. Furthermore, these models are sensitive to the layout and operation of signalized intersections. This paper discusses how conflicts are presented inside the simulation by demonstrating the mechanism of one of the conflicts. Model validation and a case study were conducted. The validation results show that the simulation model reasonably represents the occurrence of conflicts at signalized intersections, which proves that the proposed model can be a reliable approach to safety assessment. A case study compares the performance of compact intersections with wider layouts. The simulation results show trends in safety improvements, although a general conclusion cannot be made.

DOI： 10.3141/2316-14

Web of Science

Scopus

Language：Japanese   Publisher：Japan Society of Civil Engineers  

A concept of the functionally hierarchical road network has been recognized with the purpose to provide the required service for road of each class. Especially in Japan, practical use of this concept has been intensively discussed from the viewpoint of both mobility improvement of arterial roads and traffic calming in local streets. However, the impact of junctions, which is regarded as a key issue of the hierarchical road network, has not been quantitatively evaluated with the performance of individual roads and further the entire network at planning stage. Therefore, in this paper, a methodology to evaluate the impacts of junction types on the performance of the network is developed by considering junction delay into user equilibrium assignment. By applying it, case studies with hypothetical grid network showed that reduction in junction delays at arterial roads is significant to realize hierarchical road network; and if it is achieved, traffic calming in local roads can also effectively work.

DOI： 10.2208/jscejipm.68.i_751

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Roundabouts have been focused as safer, ecological and economical grade intersection type, and the practical development of roundabouts is currently discussed in Japan.<br>As it is possible to pass through without any stopping if there is no vehicle at a circulating roadway in roundabouts, the fuel consumption may be decreased in idling or accelerating. However, the total CO₂ emission based on practical driving tests has not been reported.<br>In this study, the amount of CO₂ emission is estimated from driving tests at a test roundabout and existing signal intersection. As a result, it is shown that the total CO₂ emission from the roundabout is decreased compared to the signal intersection.

DOI： 10.2208/jscejipm.68.i_1253

CiNii Research

Publisher：International Journal of Intelligent Transportation Systems Research  

This study intends to investigate operational performance of the group-based signal control approach (GA) in Japan. A cycle-based stochastic approach incorporating the HCM 2000 delay model and Monte Carlo simulation was proposed. To facilitate its application, extensive field data was collected at 11 typical intersections in Germany and Japan to understand the variability of input variables and their correlations. A series of case studies were eventually conducted to investigate the applicability of GA under various conditions, i. e., degree of saturation (DS), split ratio (SR), and the coefficient of variation (COV) of traffic demand. Conclusions supported that the operational performance of GA deteriorated with increasing SR and decreasing DS. GA is apparently advantageous for SRs less than 0.8, COVs less than 0.2, and optimum cycle lengths greater than 90 s. © 2011 Springer Science+Business Media, LLC.

DOI： 10.1007/s13177-011-0028-y

Scopus

Publisher：Computer-Aided Civil and Infrastructure Engineering  

This article describes the development and implementation of adaptive transit signal priority (TSP) on an actuated dual-ring traffic signal control system. After providing an overview of architecture design of the adaptive TSP system, the article presents an adaptive TSP optimization model that optimizes green splits for three consecutive cycles to minimize the weighted sum of transit vehicle delay and other traffic delay, considering the safety and other operational constraints under the dual-ring structure of signal control. The model is illustrated using a numerical example under medium and heavily congested situations. The findings from a field operational test are also reported to validate and demonstrate the developed TSP system. At a congested intersection, it is found that the average bus delay and average traffic delay along the bus movement direction were reduced by approximately 43% and 16%, respectively. Moreover, the average delay of cross-street traffic was increased by about 12%. © 2010 Computer-Aided Civil and Infrastructure Engineering.

DOI： 10.1111/j.1467-8667.2010.00677.x

Web of Science

Scopus

Language：Japanese   Publisher：Procedia - Social and Behavioral Sciences  

This study investigates stochastic saturation flow rate in Japan starting from shared permissive left-turn lane. The methods used in Highway Capacity Manual 2000 and Japan Society of Traffic Engineering (JSTE) guideline were analyzed and evaluated. The comparison results show that both HCM and JSTE tend to overestimate the performed saturation flow rate in shared left-turn lane. As for detailed analysis, lane blockage probability is interpreted by using a binary logistic regression model. Then an empirical model is proposed to test the effect of lane blockage and significant influencing factors on saturation flow rate estimation in shared left-turn lane. © 2011 Published by Elsevier Ltd.

DOI： 10.1016/j.sbspro.2011.04.475

Web of Science

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Quantifying the effects of signal timing and crosswalk geometry on pedestrian speed is an important requirement for improving existing operational policies and for providing a rational safety assessment at signalized intersections. The objective of this paper is to macroscopically investigate the effects of signal timing, crosswalk length and pedestrian origin-destination on pedestrian speed at signalized crosswalks. Three signalized crosswalks in Nagoya City are videotaped. A pre-developed data processing program is utilized to extract speed data. Pedestrian signal timing is divided into six intervals. Depending on the entering time, each pedestrian is assigned to one of the intervals. Then the speed distributions in different time interval are estimated and compared. Generally, it is concluded the entering speeds of pedestrians increase as pedestrian green interval proceeds. Moreover, pedestrians show higher travel speeds at long crosswalks.

DOI： 10.11175/eastpro.2011.0.105.0

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

This paper investigates urban expressway capacity characteristics of lane closure sections due to accidents. Methodology includes the following parts: 1) identification of a breakdown due to an accident, 2) estimation of capacity under accident conditions, 3) exploring features of capacity drop percentage, and 4) fitting probability distribution of capacity drop percentage. Accident record data and loop detector data on Odaka Route of Nagoya Expressway during three years are utilized to fulfill the investigation. The results reveal that mean capacity value increases and its variance turns to be convergent with increase of lane closure duration. Accident types like multiple rear-end collisions and rear-end collisions result in comparatively greater values of capacity drop percentage. Also accidents on curve segments bring relatively higher capacity drops compared with those on straight segments. Furthermore, capacity drop percentage is shown to be stochastic, and Beta distribution can well fit its probability distribution.

DOI： 10.11175/easts.9.1286

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The signal change and clearance intervals, more specifically the all-red times, are often set longer than necessary in Japan. Too long all-red times not only increase lost time but also may induce aggressive pass and lead to safety drop. Hence, the objective of this study is to investigate the impacts of intersection geometry, signal control, and traffic conflicts on driver's start-up behavior during the signal change and clearance intervals. By using extensive field data, stochastic models are developed for estimating the distributions of starting response time (SRT) and acceleration rate of the entering vehicles. A numerical examination is performed to explore the possibility of reducing the length of all-red times when the aforementioned impacts on start-up behavior are incorporated into the calculation procedure. Conclusions support that the minimum required all-red times can be reduced by 1 second.

DOI： 10.11175/eastpro.2011.0.306.0

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The number of pedestrian injuries and fatalities involved by left-turning vehicles (in left-hand traffic) at signalized intersections occupies a very large portion in traffic accidents. Installing channelization islands, e.g. raised islands or zebra marking islands at intersections is considered as one of the most important factors influencing on conflicts between pedestrians and left-turning vehicles. However, their impacts on vehicle maneuvers have not been quantitatively analyzed. The objective of this study, therefore, is to quantitatively evaluate the impacts of channelization islands, on maneuvers of left-turning vehicles. Results of the analyses on turning vehicle maneuvers conclude that the use of raised islands gives between one-and-a-half to two times greater impacts on the trajectory and the speeds as compared to the impacts of zebra islands. The use of zebra marking islands has low influence on the vehicle trajectory and the speed.

DOI： 10.11175/easts.9.1938

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Existing signal control strategies do not consider pedestrian flows in optimizing signal parameters, which may impose significant delays on pedestrians. This study aims to investigate the rationality and effectiveness of designing signal coordination for pedestrians. A Japanese numerical case study is analyzed. Field survey is conducted to collect the geometric characteristics, signal timings and vehicular traffic condition information. In a parallel approach, the performances of signal coordination for vehicular and pedestrian traffic are estimated by using the vehicular simulation tool Synchro/SimTraffic and the pedestrian simulation tool NOMAD. The results showed that the coordination for the major pedestrian flow led to a significant reduction in average delay (15%). Generally, it is concluded that the effectiveness of pedestrian signal coordination is not guaranteed but depends on the relationship between pedestrian platoon dispersion and the signal cycle length.

DOI： 10.11175/eastpro.2011.0.225.0

CiNii Research

Language：English   Publisher：Japan Society of Civil Engineers  

 Evaluation of impacts of congestion improvement scheme s on travel time reliability is very significant for road authorities since travel time reliability repr esents operational performance of expressway segments. In this paper, a methodology is presented to estimate travel tim e reliability prior to implementation of congestion relief schemes based on travel time variation modeling as a function of demand, capacity, weather conditions and road accident s. For subject expressway segmen ts, traffic conditions are modeled over a whole year considering demand and capacity as random variables. Patterns of demand and capacity are generated for each five minute interval by appl ying Monte-Carlo simulation technique, and accidents are randomly generated based on a model that links acci dent rate to traffic conditions. A whole year analysis is performed by comparing de mand and available capacity for each scenario and queue length is estimated through shockwave analysis for each time in terval. Travel times are estimated from refined speed-flow relationships developed for intercity expressways and buffer time index is estimated consequently as a measure of travel time reliability. For validation, estimated reliability indices are compared with measured values from empirical data, and it is shown that the proposed method is suitable for operational evaluation and planning purposes.

DOI： 10.2208/jscejipm.67.283

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Although several safety countermeasures such as reforming intersection layouts have been implemented, methods to evaluate their effects prior to installation has not yet been established. One of the important safety issues at signalized intersections is the interaction between left-turning vehicles (left-hand traffic) and pedestrians/cyclists. This paper aims to analyze and model the trajectory variations of left-turning vehicles. Vehicle trajectories are collected at several signalized intersections with various traffic and geometric characteristics by video observations. The analysis reveals a significant variation in trajectories depending on intersection angle, number of exit lanes and vehicle type. For modeling individual vehicle trajectories and their distribution, the Euler-spiral-based approximation methodology is applied. Model validation showed that estimated trajectory distributions explain well the spatial maneuver of left-turning vehicles.

DOI： 10.11175/easts.9.1543

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Although several safety countermeasures such as reforming intersection layouts have been implemented, methods to evaluate their effects prior to installation has not yet been established. One of the important safety issues at signalized intersections is the interaction between left-turning vehicles (left-hand traffic) and pedestrians/cyclists. This paper aims to analyze and model the trajectory variations of left-turning vehicles. Vehicle trajectories are collected at several signalized intersections with various traffic and geometric characteristics by video observations. The analysis reveals a significant variation in trajectories depending on intersection angle, number of exit lanes and vehicle type. For modeling individual vehicle trajectories and their distribution, the Euler-spiral-based approximation methodology is applied. Model validation showed that estimated trajectory distributions explain well the spatial maneuver of left-turning vehicles.

DOI： 10.11175/eastpro.2011.0.309.0

CiNii Research

Publisher：Japan Society of Civil Engineers  

 A divided two-way two-lane (TWTL) expressway crosssection was defined in the most recent update of Road Structure Ordinance in 2003. This novel structure is expected to contribute to saving building cost of rural expressways particularly with low traffic demands. However, since its speed performance is remained unclear, the expected target speed may not be realized under some road traffic conditions.<br> This paper therefore aims to analyze impacts of various conditions on speed-flow relationships of the divided TWTL expressway sections by using vehicle detector data, towards implementing the performance-oriented planning and design policy. After extensive analyses on several influencing factors that affect speed performance such as heavy vehicle ratio and precipitation, speed-flow relationships under different conditions are finally formulated. By using the proposed formulae, speed performance of the TWTL expressway sections can be verified at the planning and design stage of highways.

DOI： 10.2208/jscejipm.67.261

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Station plazas are important interchanges in the transportation network. However in Japan, their performance is reduced due to insufficient consideration of K&R behavior. Accordingly this study aims to analyze K&R vehicle stopping characteristics by investigating influencing factors such as facility configuration and plaza structure. Based on empirical data, the stopping position choice is modeled. Also different influencing factors are found for picking-up and dropping-off vehicles. Furthermore, a case study is conducted by simulation to represent the stopping position choice influenced by barrier or facility configuration.

DOI： 10.2208/jscejipm.67.67_i_1079

CiNii Research

Publisher：Japan Society of Civil Engineers  

 In this paper, a methodology to evaluate impacts of implementing auxiliary passing lanes on the qulity of service of two-way two-lane (TWTL) highways is developed, by adopting follower density as a measure of effectiveness. It aims to quantitatively esti mate the performance of traffic flows to be realized dependent on the passing lane length and its spacing and to provide suggestions as a design guide. Relationships between passing lane length, one-lane section length and follower density are formulated by modeling the simulation results based on traffic fl ow surveys. And possible combinations of minimum required passing lane length and its spacing required for achieving the target performance are indicated. Furthermore, the expected qulity of service of traffic flow under seve ral typical design policies of 2+1 lane highways are evaluated by applying this concept.

DOI： 10.2208/jscejipm.67.270

CiNii Research

Publisher：Japan Society of Civil Engineers  

 The highway traffic congestion is one of the most important social and technical issues from the early days of motorization in Japan. Accordingly, the highway capacity has long been a major concern of traffic engineers, not only in research but also in practice, in order to alleviate the traffic congestions. Also, the concept of the quality of service of traffic flow and its proper understanding according to diverse conditions are crucial for implementing the performance-oriented highway planning and design schemes. This article therefore overviews the recent research works regarding highway capacity and quality of service particularly in Japan, after reviewing the state of the arts in bottleneck phenomena observed on Japan motorways and highways. And the future perspective of these research fields is discussed.

DOI： 10.2208/jscejipm.67.217

CiNii Research

Language：Japanese   Publisher：Japan Society of Civil Engineers  

 Quality of road traffi c in Japan is still unsatisfactory as the road network cannot achieve the desirable performance corresponding to traffi c and access functions of roads yet, and there remain a lot of subjects to be resolved in terms of road design and traffi c operations. The existing road network should be gradually improved and restructured as cost-effective, high-performance one, however, the conventional highway planning and design methodology can be considered to hardly achieve it. For that, practical application of the "performance-oriented highway planning and design" policy is needed, which can flexibly adopt possible combinations of road design and traffi c operation schemes necessary for realizing target performance. In this article, for the special issue on "performance-oriented highway planning and design", its concept and research requirements are overviewed, as well as the structure of this issue.

DOI： 10.2208/jscejipm.67.195

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

In Japan, where vehicles travel on the left side of the road, the queue discharge rates of shared left-turn lane usually show comparable fluctuation, due to different departure characteristics of through and left-turning vehicles as well as interactions with pedestrians and bicycles. For a better evaluation of signalized intersections and then corridor performance, this study investigates stochastic queue discharge rates starting from shared left-turn lane and empirically explores its implications. Results show that efficient utilization of shared lane by through traffic can significantly improve discharge rate. At lower and higher pedestrian-bicycle volumes, discharge rates are relatively reliable. While at middle levels of pedestrian demands, more random arrivals and interactions lead to rather unstable saturation flow rate fluctuation. For the shared lane with a larger left turning radius, its discharge rates display a stable trend.

DOI： 10.11175/eastpro.2011.0.300.0

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

In Japan, where vehicles travel on the left side of the road, the queue discharge rates of shared left-turn lane usually show comparable fluctuation, due to different departure characteristics of through and left-turning vehicles as well as interactions with pedestrians and bicycles. For a better evaluation of signalized intersections and then corridor performance, this study investigates stochastic queue discharge rates starting from shared left-turn lane and empirically explores its implications. Results show that efficient utilization of shared lane by through traffic can significantly improve discharge rate. At lower and higher pedestrian-bicycle volumes, discharge rates are relatively reliable. While at middle levels of pedestrian demands, more random arrivals and interactions between pedestrians and vehicles lead to rather unstable saturation flow rate fluctuation. For the shared lane with a larger left turning radius, its discharge rates display a stable trend. A comparative analysis between observed saturation flow rates, Highway Capacity Manual (HCM, 2000) and Japanese guideline (JSTE, 2007) estimations indicate both HCM and Japanese guideline usually overestimate the discharge rates in shared left-turn lane in Japan.

DOI： 10.11175/easts.9.1499

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The number of pedestrian injuries and fatalities involved by left-turning vehicles (in left-hand traffic) at signalized intersections occupies a very large portion in traffic accidents. Installing channelization islands, e.g. raised islands or zebra marking islands atintersections is considered as one of the most important factors influencing on conflicts between pedestrians and left-turning vehicles. However, their impacts on vehicle maneuver have not been quantitatively analyzed. The objective of this study, therefore, is to quantitatively evaluate the impacts of channelization islands, on maneuvers of left-turning vehicles. Results of the analyses on turning vehicle maneuvers conclude that the use of raised island gives between one-and-a-half to two times greater impacts on the trajectory and the speeds as compared to the impacts of zebra islands. The use of zebra marking islands has low influence on the vehicle trajectory and the speed.

DOI： 10.11175/eastpro.2011.0.380.0

CiNii Research

Publisher：IATSS Research  

Among various pedestrian facilities, signalized crosswalks are the most complex and critical ones. Their geometry and configuration including width, position and angle directly affect the safety, cycle length and resulting delays for all users. Existing manuals do not provide clear and rational specifications for the required crosswalk width under different pedestrian demand combinations and properties. Furthermore, they do not consider the bi-directional flow effects on crossing speed and time when addressing pedestrian flow at signalized crosswalks. However, quantifying the effects of such interactions on the behavior of pedestrian flow is a prerequisite for improving the geometric design and configuration of signalized crosswalks. The objective of this paper is to develop a methodology for estimating the required crosswalk width at different pedestrian demand combinations and a pre-defined LOS. The developed methodology is based on theoretical modeling for total pedestrian platoon crossing time, which consists of discharge and crossing times. The developed models are utilized to generate the fundamental diagrams of pedestrian flow at signalized crosswalks. A comprehensive discussion about the effects of bi-directional flow and various pedestrian age groups on the characteristics of pedestrian flow and the capacity of signalized crosswalks is presented. It is found that the maximum reduction in the capacity of signalized crosswalks occurs at roughly equal pedestrian flows from both sides of the crosswalk. By utilizing existing LOS thresholds for pedestrian flow at signalized crosswalks, the required crosswalk widths for various pedestrian demand combinations are proposed for implementation. © 2010 International Association of Traffic and Safety Sciences.

DOI： 10.1016/j.iatssr.2010.06.002

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Existing manuals do not provide clear specifications for the required crosswalk width under different pedestrian demand volumes and characteristics. However, optimizing crosswalk configurations including width is an important concern to improve the overall performance of signalized intersections. The objective of this paper is to develop a methodology for estimating minimum required crosswalk width at different pedestrian demand volumes considering bi-directional flow and different pedestrian age groups. The developed methodology is based on modeling total pedestrian platoon crossing time which consists of discharge and crossing times. Discharge time is modeled by using shockwave theory while crossing time is modeled by applying aerodynamic drag theory. The developed models are then calibrated for crosswalks with mainly elderly or pupil pedestrian platoons. A set of criteria based on pedestrian crossing speed is developed to identify the minimum required crosswalk width. Finally, different required crosswalk widths are proposed for different pedestrian demand volumes and directional split ratios considering the effects of pupil and elderly pedestrian platoons.

DOI： 10.11175/eastsats.1.181

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

For a follower-based service measure to be effectively used for two-lane highway quality of service evaluation, a more reliable follower identification procedure is necessary. Current follower recognition methodologies are based on single critical headway values that may not accurately identify followers since they do not take into account the randomness of preferred tracking headways and drivers' desired speeds. This paper presents an improved, probability-based follower identification methodology that takes both of these factors into account while also considering their variability across different driving conditions. The calculated follower percentage and follower density values were compared with those estimated using the 3-second threshold suggested by the HCM. The proposed methodology estimated more followers, particularly during periods of heavy flow, highlighting the inability of using a single headway value to correctly identify followers. The resulting follower counts have been normalized, making it possible to theoretically identify followers at any given time or driving condition.

DOI： 10.11175/easts.8.1822

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publisher：Transportation Research Record  

This study presents a probabilistic safety estimation approach based on traffic conflict technique. The study aims to investigate the impacts of the German signal control policy and intergreen design method on safety during intergreen intervals at signalized intersections in Japan. To facilitate application of the policy, the uncertainty of input variables and of safety itself, indicated by the postencroachment time, was analyzed first by means of field data collected at 12 typical intersections in Japan and Germany. A few case studies were then examined with Monte Carlo simulation. The results indicated that safety during the intergreen interval and its reliability might significantly drop if intergreen times were simply changed from the values based on the Japanese method to the values based on the German method without supplementary countermeasures. However, safety as well as reliability can be maintained if the Japanese control policy is completely replaced with the German one.

DOI： 10.3141/2128-23

Web of Science

Scopus

Language：Japanese   Publisher：Transportation Research Record  

Preevaluation of the impacts of congestion relief schemes on travel time reliability is significant for road authorities. However, most existing approaches to estimating travel time reliability rely mainly on empirical data and are therefore not of help for evaluating improvement schemes before implementation. A methodology is presented to estimate travel time reliability on the basis of modeling travel time variations as a function of demand, capacity, weather conditions, and road accidents. For a subject expressway segment, patterns of demand and capacity were generated for each 5-min interval during a year by using the Monte Carlo simulation technique, and accidents were generated randomly according to traffic conditions. A whole year analysis was performed by comparing demand and available capacity for each scenario; shock wave analysis was used to estimate the queue length at each time interval. Travel times were estimated from refined speed-flow relationships. The buffer time index was estimated as a measure of travel time reliability and compared with observed values from empirical data. After validation, the methodology was applied to assess the impact on travel time reliability of opening the hard shoulder to traffic. Opening the hard shoulder to traffic during the peak periods was found to ameliorate travel time reliability significantly and mitigate congestion levels, which could result in up to a 26% cut in the number of accidents occurring.

DOI： 10.3141/2124-13

Web of Science

Scopus

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Current follower recognition methodologies are based on single critical headway values that may not accurately identify followers since they do not take into account the randomness of preferred tracking headways and drivers desired speeds. This paper presents an improved, probability-based follower identification methodology that takes both of these factors into account while also considering their variability across different driving conditions. The calculated follower percentage and follower density values were compared with those estimated using the 3-second threshold suggested by the HCM. The proposed methodology estimated more followers, particularly during periods of heavy flow, highlighting the inability of using a single headway value to correctly identify followers. The resulting follower counts have been normalized, making it possible to theoretically identify followers at any given time or driving condition.

DOI： 10.11175/eastpro.2009.0.338.0

CiNii Research

Publisher：16th ITS World Congress  

This paper presents the evaluation results on operational and safety performance of group-based signal control, based on a field test undertaken in Japan recently. Starting response time (SRT), start-up lost time (SULT), clearance lost time (CLT), saturation flow rate (SFR), and approach delay (AD) are selected to represent operational performance. Certain occurrence frequencies and rates of stop-line crossing during amber (SCA) and red-light-running (RLR) act as the measures to safety performance during intergreen intervals. The results from the before-and-after analyses supported that the group-based control itself generally didn't significantly affect SRT, SULT, CLT, and SFR, while remarkably improved AD. Meanwhile, it substantially decreased SCA and RLR at the exclusive through and right-turn lanes. It reveals that both operational and safety benefits might be expected by applying such a policy.

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

Existing manuals do not provide clear specifications for the required crosswalk width under different pedestrian demands and properties. However, optimizing crosswalk configurations including width is an important concern to improve the overall performance of signalized intersections. The objective of this paper is to develop a methodology for estimating minimum required crosswalk width at different pedestrian demands considering bi-directional flow and different pedestrian age groups. The developed methodology is based on modeling total pedestrian platoon crossing time which consists of discharge and crossing times. Discharge and crossing times are modeled by using shockwave and aerodynamic drag theories respectively. Then developed models are calibrated for crosswalks with elderly or pupil pedestrian platoons. A criteria based on pedestrian crossing speed is developed to identify the minimum required crosswalk width. Finally, different minimum required crosswalk widths are proposed.

DOI： 10.11175/eastpro.2009.0.222.0

CiNii Research

Publisher：Proceedings of the 7th International Conference of Chinese Transportation Professionals Congress 2007: Plan, Build, and Manage Transportation Infrastructures in China  

An official nationwide manual on intersection planning and design remains absent in China. Presently, a research group led by Tongji University is addressing its first version. Toward gaining more profound knowledge on state of the art in intersection design and operations in overseas while developing Chinese manual, this paper thus presents German and Japanese experiences. Conclusions, future studies and efforts essential for China are discussed finally. © 2008 ASCE.

DOI： 10.1061/40952(317)51

Scopus

Language：English  

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Language：Japanese   Publisher：Transport Reviews  

In transport terms, Japan has an enviable reputation for operating effectively an incredibly complex road and rail system. However, relatively little is known about how this is done or about the issues that are facing policy-makers and shapers in the country. The purpose of this paper, then, is to investigate how land passenger transport is organized in Japan, and to begin to evaluate its effectiveness. This is done by drawing on a literature review and on findings from a scoping study based on a series of semi-structured in-depth interviews with key practitioners. Overall, the findings suggest that national and local transport policy in Japan faces a number of key challenges across all modes in the land passenger transport system, in particular relating to the fragmented approach to policy development, implementation, and operation and to the growing role of the car.

DOI： 10.1080/01441640701526699

Web of Science

Scopus

Language：Japanese   Publisher：Transportation Research Record  

On a two-lane highway with passing restrictions, user dissatisfaction usually is caused by the inability to drive at the desired speed because of a relatively slower lead vehicle. Although this condition clearly shows that vehicles in this state are following, current definitions of "following vehicle" are based mainly on headway alone. A "follower" can be more logically defined as a vehicle traveling below its desired speed because of the presence of a relatively slower lead vehicle. The problem arises because the desired speeds of different drivers vary significantly; the variation makes it difficult to assess whether a vehicle is constrained on the basis of directly accessible data alone. A study was done to develop desired speed distributions for various traffic, weather, and ambient conditions, which can be later used as input for simulation or to calculate a vehicle's following probability given its current speed. The collected data were classified according to different traffic, geometric, weather, and ambient conditions to form 64 data sets for analysis. The desired speed distributions were estimated by using the modified Kaplan-Meier approach and were found to be suitable for use as either simulation input or as a tool that can be used for follower identification. Differences between holiday and weekday travel speed preferences and effects of weather on driver speed choices were also found.

DOI： 10.3141/2088-23

Web of Science

Scopus

Publisher：Japan Society of Civil Engineers  

The existing highways in Japan are planned and designed based on the specifications determined in the past. However, economy and improvement of traffic-performance quality are demanded in the highways recently, and the authors have been advocating traffic-performance-oriented highway planning and design. In this paper, a methodology to estimate the traffic-performance of a planned inter-city highway throughout a year was established, and a traffic-performance-oriented highway planning and design methodology was proposed. This methodology provides several options of road crosssectional design for a planned highway, and makes it possible to adopt the most economical and best performing road structure and traffic operation option based on the latest knowledge

DOI： 10.2208/journalip.25.67

CiNii Research

Publisher：IATSS Research  

Unlike the typical stage-based policy commonly applied in Japan, the group-based control (often called movement-based in the traffic control industry in Japan) refers to such a control pattern that the controller is capable of separately allocating time to each signal group instead of stage based on traffic demand. In order to investigate its applicability at signalized intersections in Japan, an intersection located in Yokkaichi City of Mie Prefecture was selected as an experimental application site by the Japan Universal Traffic Management Society (UTMS). Based on the data collected at the intersection before and after implementing the group-based control policy respectively, this study evaluated the impacts of such a policy on driver behavior and intersection safety. To specify those impacts, a few models utilizing cycle-based data were first developed to interpret the occurrence probability and rate of red-light-running (RLR). Furthermore, analyses were performed on the yellow-entry time (Ye) of the last cleared vehicle and post encroachment time (PET) during the phase switching. Conclusions supported that the group-based control policy, along with certain other factors, directly or indirectly influenced the RLR behavior of through and right-turn traffics. Meanwhile, it has potential safety benefits as well, indicated by the declined Ye and increased PET values. © 2008 International Association of Traffic and Safety Sciences.

DOI： 10.1016/S0386-1112(14)60211-9

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publisher：Transportation Research Record  

This paper aims to investigate the breakdown phenomenon at on-ramp merging sections of urban expressways in Japan. The breakdown events are treated here as a probabilistic phenomenon. Six merging sections at which breakdowns frequently occur are selected to be different in their geometry in relation to acceleration lane length and ramp entrance side. Three different aspects of merging capacity are recognized: the maximum outflow rate before the breakdown, the outflow rate when the breakdown starts to occur, and the outflow rates during the queue discharge period. These outflow aspects are analyzed after they are converted into an equivalent passenger car unit to eliminate the effect of heavy vehicles. Then the probability of breakdown at these sections is investigated as a function of outflow rates. The observed breakdown probabilities follow the Weibull distribution function at all sections, with close values of shape parameter and wide range values of scale parameter. The values of the scale parameter are used to investigate the effects of the acceleration lane length and entrance ramp side. Moreover, the breakdown probability is investigated as a function of the occupancy observed immediately downstream of the merging section. Last, the effects of ramp flow ratio and interval length of aggregated data are discussed.

DOI： 10.3141/2012-02

Web of Science

Scopus

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The authors are currently investigating the applicability of the operation policy, commonly applied at signalized intersections in Germany, for Japanese signalized intersections. As an initial step, this study analyzed traffic characteristics and driver behavior at several typical German and Japanese intersections to understand the impacts of such policy on them. The results showed that German intersections had significantly lower starting response time (SRT) and start-up lost time (SULT), which was due to the sequence of signal indications. However, no apparent variations existed in saturation flow rate (SFR) and lost time in amber (LTA). Left turners at German intersections tended to be more aggressive in choosing suitable gaps, indicated by critical gap and 1/PET values. Moreover, longer all-red clearance interval and gap adaptive control seemed to encourage aggressive pass. Lower stop-line crossing during amber (SCA) and red light violation (RLV) rates at German intersections were attributed to multiple factors.

DOI： 10.11175/eastpro.2007.0.324.0

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The authors have advocated a new planning and design methodology in for highways in Japan, which includes operational performance check in consideration of the traffic demand fluctuation. For this method, it is necessary to reproduce the hourly traffic demand fluctuation on a planned and designed highway section throughout a year. This study proposes a method to reproduce it with two phases; reproducing the daily traffic demand phase and setting the hourly traffic demand coefficient phase, in consideration of potential hourly traffic demand on a day with congestion. The reproduced hourly traffic demand fluctuation using this method was validated on two expressway sections in Japan. As a result, we could verify that the reproduction precision was satisfactory except that it could not consider some special local characteristics.

DOI： 10.11175/eastpro.2007.0.277.0

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

A roundabout is an alternative type of junction control that reduces delay under low traffic demand. Conditions under which they are advantageous in terms of capacity and delay have been already shown in existing researches. However, the implementation of roundabouts is likely to be negatively evaluated, particularly in Japan; due to safety reasons since traffic conflicts are inevitable when merging. In this paper, a methodology for the performance evaluation of at-grade junctions considering a trading-off relationship between delay and vehicular conflicts is proposed. The performance of signalized intersections and roundabouts are also compared by applying this methodology. As a result, it was found that roundabouts are still more advantageous than signalized intersections when approaching traffic volume is less than 500 vph, even though not only delay but also conflicts were taken into account as evaluation indices.

DOI： 10.11175/easts.7.2412

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

This paper introduces some applications of travel time based performance measures and mainly the travel time reliability as a measure of performance. In this research, operational conditions of two different segments of an intercity expressway are evaluated and compared by using travel time based performance measures. While Buffer Time Index and Travel Time Index are used to evaluate travel time reliability and congestion, it is observed that travel times are more reliable during off-peak periods, whereas unreliability dramatically increases during the peak periods. Additionally, travel time reliability varies from time to time according to demand fluctuations and traffic influencing events. Finally, highway segments are found to be more susceptible to disruptions caused by traffic influencing events once congestion starts to build up.

DOI： 10.11175/eastpro.2007.0.318.0

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The effects of heavy vehicles become more pronounced in two-lane highway facilities with passing restrictions since vehicles in a platoon do not have any other choice but to follow the leaders’ choice of speed, which is usually below their desired speed levels. Furthermore, platoon lengths are expected to be longer than usual, affecting level of service indicators such as follower density and average travel speed. This study aims to make a preliminary analysis of the influence of heavy vehicle on such facility types in Japan. Detector data were analyzed for two different time periods — peak and weekday. The speed of heavy vehicles has a direct effect on follower speed and follower density was found to become more sensitive to heavy vehicle percentage as flow rate increases. Average speed was also found to be more sensitive to heavy vehicle presence on upgrades, especially during the evening period.

DOI： 10.11175/easts.7.2533

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The effects of heavy vehicles become more pronounced in two-lane highway facilities with passing restrictions since vehicles in a platoon do not have any other choice but to follow the leaders' choice of speed, which is usually below their desired speed levels. Furthermore, platoon lengths are expected to be longer than usual, affecting level of service indicators such as follower density and average travel speed. This study aims to make a preliminary analysis of the influence of heavy vehicle on such facility types in Japan. Detector data were analyzed for two different time periods - peak and weekday. The speed of heavy vehicles has a direct effect on follower speed and follower density was found to become more sensitive to heavy vehicle percentage as flow rate increases. Average speed was also found to be more sensitive to heavy vehicle presence on upgrades, especially during the evening period.

DOI： 10.11175/eastpro.2007.0.330.0

CiNii Research

Language：English   Publisher：Eastern Asia Society for Transportation Studies  

The authors are currently investigating the applicability of the operation policy, commonly applied at signalized intersections in Germany, for Japanese signalized intersections. As an initial step, this study analyzed traffic characteristics and driver behavior at several typical German and Japanese intersections to understand the impacts of such policy on them. The results showed that German intersections had significantly lower starting response time (SRT) and start-up lost time (SULT), which was due to the sequence of signal indications. However, no apparent variations existed in saturation flow rate (SFR) and lost time in amber (LTA). Left turners at German intersections tended to be more aggressive in choosing suitable gaps, indicated by critical gap and 1/PET values. Moreover, longer all-red clearance interval and gap adaptive control seemed to encourage aggressive pass. Lower stop-line crossing during amber (SCA) and red light violation (RLV) rates at German intersections were attributed to multiple factors.

DOI： 10.11175/easts.7.2470

CiNii Research

Publisher：Japan Society of Civil Engineers  

The authors have been advocating performance-oriented highway planning and design methodology in Japan. For this, it is necessary to estimate the hourly traffic demand fluctuation on a planned highway section throughout a year. This study proposes a method to estimate it within two phases; estimating the daily traffic demand phase and setting the hourly traffic demand coefficient phase, in consideration of potential hourly traffic demand. Estimates for each category, corresponding to road characteristics can be calculated using this method. This procedure enables the performancecheck of any planned highway sections throughout a year by inputting traffic demand into the respective design performance curve.

DOI： 10.2208/journalip.24.825

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Language：English  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：English  

Language：English  

Authorship：Lead author   Language：English  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

CiNii Research

Language：Japanese   Publisher：国際交通安全学会  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English  

Language：Japanese   Publisher：Transportation Research Record  

Two-lane expressways exist as provisional sections for future expansion to four-lane expressways in Japan, although recently such roadway types have been considered for construction for permanent use. Their highway classification may fall somewhere between common (multilane) expressways and ordinary two-lane highways, with full access control and high speed limits but with only one lane per direction of travel. Since this type of highway is unique, methodologies for service level measurement of other uninterrupted-flow facilities are not applicable. Percent time spent following, for instance, is estimated with significant consideration of the opposing flow rate, which has practically no effect on driving conditions since a median barrier is present in all sections. The goal of this study is to analyze and compare possible performance measures that would best describe the traffic operational characteristics of two-lane expressways. Among the performance measures considered, follower density had much promise, having shown strong relationships with flow rate. Since the available data were only those taken during off-peak periods, further observations of follower flow must be made during congested or near-congested flow to establish follower density and volume relationships for all traffic conditions.

DOI： 10.3141/1988-16

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Scopus

Language：Japanese   Publisher：Japan Society of Civil Engineers  

In the field of traffic engineering, video image analysis is an essential technique for correct understanding of traffic phenomena and has been often used for many purposes. However, manual use of this type of technique is a very labor-intensive work. In this study, a multi-functional video image processing system is developed, which can 1) count traffic volumes, 2) track moving objects such as vehicles and pedestrians, and 3) recognize license plates automatically by using image processing technology. Case studies are carried out by applying this system to the actual road traffic, and its performance and accuracy are evaluated. In conclusion, the developed system showed sufficiently satisfactory performance for practical use.

DOI： 10.2208/jscejd.62.276

CiNii Research

Publisher：13th World Congress on Intelligent Transport Systems and Services  

This paper presents the overview of an integrated video image processing system which can count traffic volumes, track moving objects such as vehicles and pedestrians, and recognize license plates number automatically by using image processing technology without any special hardware. Case studies are carried out by applying this system to the actual road traffic scene, and its performance and accuracy are evaluated. Experimental results of the image processing show that each analysis function has sufficiently satisfactory performance for practical use.

Scopus

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

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Language：Japanese  

Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscej.2004.772_1

CiNii Research

Language：English  

Language：English  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Language：English  

Language：English  

Authorship：Lead author   Language：English  

Publisher：Proceedings of the International Conference on Applications of Advanced Technologies in Transportation Engineering  

This study aims to analyze the mechanism of risky behavior at inter-green periods and to develop a "behavior risk estimation model" which reflects driver's perception for evaluating cycle length under under-saturated traffic conditions. The risky behaviors at the inter-green period are expressed by a disaggregate logit model for each movement (through, right-rum, left-turn) using field survey data. These models are explained by delay and various traffic conflicts, which are influenced by cycle lengths. The estimated parameters of these models quantitatively indicate that longer cycle length induces more risky behaviors at inter-green periods.

DOI： 10.1061/40730(144)39

Scopus

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English  

Authorship：Lead author   Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English  

Authorship：Lead author   Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

Language：Japanese  

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Publisher：Japan Society of Civil Engineers  

For the planning of the park-and-ride (P&R) strategy in urban areas, it is necessary to estimate the P&R demand appropriately corresponding to the conditions of the policy measure, i. e. size, location and charge of the P&R facilities. In addition, traffic flow conditions caused by the change in demand must be also evaluated. In this study, a modal choice model which includes the access mode choice behavior is developed and change in the demand is expressed by that. A microscopic traffic flow simulation model is also developed in order to express the spatial distribution of the traffic flow conditions dynamically. By combining these models and adding the dynamic park-and-ride (DP&R) choice model to that, a P&R strategy evaluation system is structured, which enables to simulate the entire intermodal trip from origin to destination and the traffic flow in the network. Furthermore, applying this system to the eastern part of Nagoya City, effects by the P&R related measures such as settlement of parking facilities and DP&R are discussed.

DOI： 10.2208/journalip.18.795

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Publisher：Japan Society of Civil Engineers  

This study tries to assess the quality of service of a basic motorway section based on the driver's perception, which is one of the noticeable concerns in the discussion on the quality of service. A field driving survey in a rural motorway section is conducted, in order to collect data on driver's degree of satisfaction under various traffic flow conditions. It is fuither analyzed how these measured values of degree of driver's satisfaction relate to the traffic flow conditions and driving behaviors, and the interrelationship among them is quantitatively described. In addition, setting the level of service based on the average satisfaction degree was tried and was compared with the conventional ones. The result suggests that the traffic condition in motorways, which is assumed in the current Japanese planning procedure, may hardly satisfy the drivers.

DOI： 10.2208/journalip.17.941

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publisher：土木学会  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

Publisher：Japan Society of Civil Engineers  

This paper describes an assessment of effects by introducing the Dynamic Park and Ride (DP&R) system, which is a typical application of the ITS technology to the intermodal travel management A DP&R choice behavior model is developed, using SP data surveyed by authors in the eastern area of Nagoya City and its vicinity.This choice model is incorporated into a traffic simulation and several scenarios on combinations of policy options for the DP&R are examined.Consequently, it was quantitatively found that some policy options related to improvement of services for P&R should be enforced simultaneously, so that the DP&R system may contribute to reduction of car trips.

DOI： 10.2208/journalip.16.949

CiNii Research

Publisher：Japan Society of Civil Engineers  

The highway level of service plays an important role to determine the highway cross-sectional structure. This study aims at setting the level of service based on estimation of the minimal life cycle cost (LCC), under various geographical and traffic demand conditions. The level of service of the alternative cross-sectional structures which achieve the minimal LCC is quantitatively estimated in terms of volume to capacity ratio. As a result, the tendency is found that the higher graded design gives the smaller LCC. It is also shown that the level of service currently applied in Japan is between the values set by the minimal LCC and the minimal extended-life-cycle-CO<SUB>2</SUB> criteria.

DOI： 10.2208/journalip.16.933

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Publisher：Japan Society of Civil Engineers  

Effective measures against the rapid growth in CO2 emission from Japanese transport sector is urgently needed. However, definite target values of the emission due to the transportation activities, how much and in which cities to be cut down, are not shown. This results in difficulty to make a decision of suitable transport policies. This study therefore indicates the goal values of transport options required for realization of reducing CO2 emission, setting its acceptable level in 2010. For the urban passenger transport in paiticular, it is tried to estimate the values by size of city, according to the characteristics of urban transportation activities. Several available options as a suitable transport policy for the each size of city are finally discussed.

DOI： 10.2208/journalip.15.739

CiNii Research

Publisher：Japan Society of Civil Engineers  

This paper proposes a method for the comprehensive assessment on cross-sectional structures of inter-city motorways in terms of CO<SUB>2</SUB> emission. The index employed in this study is the “Extended Life-cycle CO<SUB>2</SUB> (ELC-CO<SUB>2</SUB>)” emission from highways. This takes into account of not only the CO<SUB>2</SUB> generated by highway construction and maintenance works, but also the CO<SUB>2</SUB> emission by traffic, which varies by highway cross-sectional design. Such traffic flow characteristics as traffic flow variations and/or speed-flow relationship is also investigated, which has not been considered in the conventional studies on LCA. The CO<SUB>2</SUB> emission by highway construction and maintenance works is estimated using “combined method”, for elevated, mounded, and tunnel sections respectively. Furthermore, various cross-sectional structures by several geographical and land-use conditions are assessed, through the calculation of ELC-CO<SUB>2</SUB> from each alternative.

DOI： 10.2208/proer1988.26.261

CiNii Research

Publisher：Japan Society of Civil Engineers  

CO<SUB>2</SUB> emission from transport sector is drastically increasing, and this trend will never change without any appropriate countermeasures against that. Policies relating to reduction of CO<SUB>2</SUB> emission from transport sector are categorized by 1) stage in environmental influence mechanism, and 2) their method. On the other hand, a target value of CO<SUB>2</SUB> emission from Japanese urban passenger transport in 2010 is assumed to be the same level as that in 1990. Its value is estimated by population size of city, considering differences of transport properties and its effects on CO<SUB>2</SUB> reduction. Furthermore, required amount of each policy option for achieving the target value is calculated. Consequently, it is found that 1) no single policy option is effective, even if vehicle fuel consumption efficiency would be drastically improved, that results in necessity of combining various policy options, 2) effective measures in small cities is essential, whose transport activities are strongly dependent on automobiles and that cause about 80% of total CO<SUB>2</SUB> emission from urban passenger transport.

DOI： 10.2208/proge.6.121

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)