Faculty Profiles - NAKAMURA, Hideki

Efficiency and Safety Evaluation of Left-turn Vehicles and Crossing Pedestrians in Signalized Intersections under the Autonomous Vehicle Mixed Flow Condition

Examination of Teardrop Roundabout Geometric Design through a Field Experimental Study

OKUSHIRO Hiroshi, YOSHIOKA Keisuke, ISHIGURO Yuuki, NAKANE Takeshi, MATSUOKA Toshiaki, SHUDO Takako, ZHANG Xin, NAKAMURA Hideki, ABE Yoshinori, KANBE Nobuto, SHIMOKAWA Sumio

JSTE Journal of Traffic Engineering Vol. 8 ( 4 ) page： B_18 - B_25 2022.4

Pan, A; Zhang, X; Iryo-Asano, M; Nakamura, H

INTERNATIONAL JOURNAL OF INTELLIGENT TRANSPORTATION SYSTEMS RESEARCH Vol. 20 ( 1 ) page： 103 - 116 2022.4

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

An international comparative study on driving attitudes and behaviors based on questionnaire surveys Open Access

Suzuki, K; Tang, KS; Alhajyaseen, W; Suzuki, K; Nakamura, H

IATSS RESEARCH Vol. 46 ( 1 ) page： 26 - 35 2022.4

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

A multi-country survey for collecting and analyzing facts related to road traffic safety: Legislation, enforcement, and education for safer drivers Open Access

Toriumi A., Abu-Lebdeh G., Alhajyaseen W., Christie N., Gehlert T., Mehran B., Mussone L., Shawky M., Tang K., Nakamura H.

IATSS Research Vol. 46 ( 1 ) page： 14 - 25 2022.4

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

Modeling effects of driver safety attitudes on traffic violations in China using the theory of planned behavior Open Access

Road safety and traffic culture from an international perspective Open Access

Nakamura H., Morimoto A.

IATSS Research Vol. 46 ( 1 ) page： 1 - 2 2022.4

Tan C., Shi Y., Bai L., Tang K., Suzuki K., Nakamura H.

IATSS Research Vol. 46 ( 1 ) page： 63 - 72 2022.4

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

Investigating the attitudes of Egyptian drivers toward traffic safety Open Access

Timmermans C., Shawky M., Alhajyaseen W., Nakamura H.

IATSS Research Vol. 46 ( 1 ) page： 73 - 81 2022.4

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

International analysis on social and personal determinants of traffic violations and accidents employing logistic regression with elastic net regularization Open Access

Shiomi Y., Toriumi A., Nakamura H.

IATSS Research Vol. 46 ( 1 ) page： 36 - 45 2022.4

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

Capacity Analysis of Signalized Traffic Circles in Comparison with Conventional Intersections

BAI Yan, ZHANG Xin, NAKAMURA Hideki

Journal of the Eastern Asia Society for Transportation Studies Vol. 14 ( 0 ) page： 1958 - 1975 2022.3

Language：English Publisher：Eastern Asia Society for Transportation Studies

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.

DOI： 10.11175/easts.14.1958

Lane-based Evaluation of the Traffic Flow Quality of Service in Urban Expressway Weaving Segments Based on Lane Utilization Rate

ZHOU Zhengyang, NAKAMURA Hideki, IRYO-ASANO Miho, KAKIMOTO Yuji

Journal of the Eastern Asia Society for Transportation Studies Vol. 14 ( 0 ) page： 1870 - 1887 2022.3

Language：English Publisher：Eastern Asia Society for Transportation Studies

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.

DOI： 10.11175/easts.14.1870

Modeling of Daily Speed-Flow Relationships Considering Road Condition and Traffic Flow Variations Reviewed

KAKIMOTO Yuji, NAKAMURA Hideki

JSTE Journal of Traffic Engineering Vol. 8 ( 2 ) page： A_62 - A_72 2022.2

Language：Japanese Publisher：Japan Society of Traffic Engineers

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.

DOI： 10.14954/jste.8.2_a_62

ANALYSIS OF THE RELATIONSHIP BETWEEN DRIVERS' COGNITIONS AND UNSAFE DRIVING BEHAVIOR

Analysis on the Relationship between Roundabout Geometric Elements and Vehicle Driving Positions

NISHIGAKI Yuki, ZHANG Xin, KAKIMOTO Yuji, NAKAMURA Hideki

JSTE Journal of Traffic Engineering Vol. 8 ( 2 ) page： A_15 - A_21 2022.2

Proposal for the Degree of Hierarchy of Road Networks using Road Use Characteristic Index

SEKIHARA Toshihiro, KAKIMOTO Yuji, NAKAMURA Hideki, IRYO Miho, ZHANG Xin

Proceedings of the Conference of Japan Society of Traffic Engineers Vol. 42 ( 0 ) page： 455 - 462 2022

Analysis of the Relationship between the Structure of Road Networks and their Functionally Hierarchical Characteristics

TOMINAGA Masahiro, KAKIMOTO Yuji, NAKAMURA Hideki, SEKIHARA Toshihiro

Proceedings of the Conference of Japan Society of Traffic Engineers Vol. 42 ( 0 ) page： 463 - 469 2022

KAKO Yoko, KAKIMOTO Yuji, ZHU Hong, NAKAMURA Hideki

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 77 ( 5 ) page： I_915 - I_924 2022

Language：Japanese Publisher：Japan Society of Civil Engineers

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.

DOI： 10.2208/jscejipm.77.5_i_915

Analysis of left-turn lane capacity under autonomous vehicle mixed flow considering the influence of pedestrian volume and crosswalk length Open Access

Zhang, X; Wang, YF; Nakamura, H; Liu, KX

ASIAN TRANSPORT STUDIES Vol. 8 2022

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

Interactions between autonomous vehicles and pedestrians at unsignalized mid-block crosswalks considering occlusions by opposing vehicles

Zhu, H; Iryo-Asano, M; Alhajyaseen, WKM; Nakamura, H; Dias, C

ACCIDENT ANALYSIS AND PREVENTION Vol. 163 page： 106468 2021.12

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

A novel agent-based framework for evaluating pedestrian safety at unsignalized mid-block crosswalks

PubMed

Zhu, H; Almukdad, A; Iryo-Asano, M; Alhajyaseen, WKM; Nakamura, H; Zhang, X

ACCIDENT ANALYSIS AND PREVENTION Vol. 159 page： 106288 2021.9

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