Faculty Profiles - NAKAMURA, Hideki

Stochastic approach for modeling the effects of intersection geometry on turning vehicle paths

Alhajyaseen, WKM; Asano, M; Nakamura, H; Tan, DM

TRANSPORTATION RESEARCH PART C-EMERGING TECHNOLOGIES Vol. 32 page： 179 - 192 2013.7

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

Left-turn gap acceptance models considering pedestrian movement characteristics

Alhajyaseen, WKM; Asano, M; Nakamura, H

ACCIDENT ANALYSIS AND PREVENTION Vol. 50 page： 175 - 185 2013.1

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

Lane-Based Breakdown Identification at Diverge Sections for Breakdown Probability Modeling

PubMed

Ma, DP; Nakamura, H; Asano, M

TRANSPORTATION RESEARCH RECORD ( 2395 ) page： 83 - 92 2013

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

A Crash Risk Estimation Model for Urban Expressway Basic Segments Considering Geometry, Traffic Flow and Ambient Conditions

WU Yong, NAKAMURA Hideki, ASANO Miho

Journal of the Eastern Asia Society for Transportation Studies Vol. 10 ( 0 ) page： 1916 - 1929 2013

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

MODELING GAP CHOICE BEHAVIOR AT URBAN EXPRESSWAY MERGING SECTIONS

CHU Tien Dung, NAKAMURA Hideki, ASANO Miho

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 69 ( 5 ) page： I_881 - I_891 2013

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

Effectiveness of Signal Coordination for Pedestrian Flows Considering Bi-directional Flow Impacts

K.M. ALHAJYASEEN Wael, LI Meng, NAKAMURA Hideki, DAAMEN Winnie

Asian Transport Studies Vol. 2 ( 3 ) page： 223 - 238 2013

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

Estimation of left-turning vehicle maneuvers for the assessment of pedestrian safety at intersections Open Access

Alhajyaseen W.K.M., Asano M., Nakamura H.

IATSS Research Vol. 36 ( 1 ) page： 66 - 74 2012.7

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

Open Access

Development of Microscopic Traffic Simulation Model for Safety Assessment at Signalized Intersections

Tan, DM; Alhajyaseen, WKM; Asano, M; Nakamura, H

TRANSPORTATION RESEARCH RECORD ( 2316 ) page： 122 - 131 2012

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

EVALUATION OF THE FUNCTIONALLY HIERARCHICAL ROAD NETWORK CONSIDERING JUNCTION TYPES

GOTO Azusa, NAKAMURA Hideki, ASANO Miho

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 68 ( 5 ) page： I_751 - I_764 2012

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

A COMPARISON ANALYSIS ON CO2 EMISSION WITH ROUNDABOUTS AND SIGNALIZED INTERSECTIONS BASED ON THE DRIVING TESTS

YOSHIOKA Keisuke, YONEYAMA Yoshiyuki, MUNEHIRO Kazunori, NAKAMURA Hideki, OGUCHI Takashi

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 68 ( 5 ) page： I_1253 - I_1259 2012

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. 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. 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

Investigating Operational Benefits of Group-based Signal Control in Japan Through a Stochastic Approach

Tang K., Nakamura H.

International Journal of Intelligent Transportation Systems Research Vol. 9 ( 2 ) page： 71 - 81 2011.5

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

Modeling and Implementation of Adaptive Transit Signal Priority on Actuated Control Systems

Li, M; Yin, YF; Zhang, WB; Zhou, K; Nakamura, H

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING Vol. 26 ( 4 ) page： 270 - 284 2011.5

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

Saturation Flow Rate Analysis for Shared Left-turn Lane at Signalized Intersections in Japan

Chen Peng, Nakamura Hideki, Asano Miho

6TH INTERNATIONAL SYMPOSIUM ON HIGHWAY CAPACITY AND QUALITY OF SERVICE Vol. 16 page： 548 - 559 2011

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

ANALYSIS ON PEDESTRIAN SPEEDS AT INTERSECTIONS CONSIDEREING SIGNAL TIMING AND CROSSWALK LENGTH

Alhajyaseen Wael K. M., Zhang Xin, Nakamura Hideki, Asano Miho

Proceedings of the Eastern Asia Society for Transportation Studies Vol. 2011 ( 0 ) page： 105 - 105 2011

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

Urban Expressway Capacity Characteristics of Lane Closure Sections due to Accidents

MA Danpeng, NAKAMURA Hideki, ASANO Miho

Journal of the Eastern Asia Society for Transportation Studies Vol. 9 ( 0 ) page： 1286 - 1299 2011

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

Start-up Behavior Considering Interactions between the Clearing and Entering Vehicles during the Signal Change and Clearance Intervals

Suzuki Kazufumi, Goto Azusa, Nakamura Hideki, Tang Keshuang, Asano Miho

Proceedings of the Eastern Asia Society for Transportation Studies Vol. 2011 ( 0 ) page： 306 - 306 2011

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

Impacts of Channelization Islands on the Left-turning Vehicle Maneuvers at Signalized Intersections in Japan

TAN Dang minh, ASANO Miho, NAKAMURA Hideki

Journal of the Eastern Asia Society for Transportation Studies Vol. 9 ( 0 ) page： 1938 - 1952 2011

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

Effectiveness of Signal Coordination for Pedestrian Flows Considering Bi-directional Flow Impacts

Alhajyaseen Wael K. M., Li Meng, Nakamura Hideki, Daamen Winnie

Proceedings of the Eastern Asia Society for Transportation Studies Vol. 2011 ( 0 ) page： 225 - 225 2011

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

APPLICATION OF TRAVEL TIME RELIABILITY FOR PERFORMANCE ORIENTED OPERATIONAL PLANNING OF EXPRESSWAYS

MEHRAN Babak, NAKAMURA Hideki

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 67 ( 3 ) page： 283 - 299 2011

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