Faculty Profiles - NAKAMURA, Hideki

Methodology to Evaluate the Quality of Service of Traffic Flow on Intercity Expressway Sections by using Follower Percentage

Konda, H; Nakamura, H

TRANSPORTATION RESEARCH RECORD Vol. 2674 ( 6 ) page： 200 - 210 2020.6

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

Introducing a multi-variate classification method: Risky driving acceptance among different heterogeneous driver sub-cultures

Timmermans, CPM; Alhajyaseen, WKM; Ross, V; Nakamura, H

JOURNAL OF SAFETY RESEARCH Vol. 73 page： 81 - 91 2020.6

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

Modeling the Impact of Downstream Conditions on Discharging Behavior of Vehicles at Signalized Intersections Using Micro-Simulation

PubMed

Zhu, H; Nakamura, H; Alhajyaseen, W

ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING Vol. 45 ( 5 ) page： 4187 - 4202 2020.5

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

Modeling Traffic Flows on Urban Arterials Considering the Downstream Influence

Zhu, H; Nakamura, H; Alhajyaseen, W; Iryo-Asano, M

TRANSPORTATION RESEARCH RECORD Vol. 2674 ( 5 ) page： 475 - 485 2020.5

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

Examination on Measuring Quality of Service Considering Car-Following Condition on Intercity Expressways Reviewed

KONDA Hiroyuki, NAKAMURA Hideki

JSTE Journal of Traffic Engineering Vol. 6 ( 2 ) page： A_9 - A_15 2020.2

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

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.

DOI： 10.14954/jste.6.2_a_9

Impact of Considering Signalized Intersection Density in the Flow-Speed Formula on Benefit Estimation of Road Projects Reviewed

KAKIMOTO Yuji, NAKAMURA Hideki

JSTE Journal of Traffic Engineering Vol. 6 ( 2 ) page： A_198 - A_205 2020.2

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

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.

DOI： 10.14954/jste.6.2_a_198

A Study on using Free Speed for Estimating Expressway Quality of Service Reviewed

AKANDWANAHO Edwin, NAKAMURA Hideki

JSTE Journal of Traffic Engineering Vol. 6 ( 2 ) page： A_244 - A_253 2020.2

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

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, FSI = AS/FS as an indicator of expressway QOS perception. FSI was found to decrease with an increase in traffic flow, and its potential applications are discussed.

DOI： 10.14954/jste.6.2_a_244

追従車構成率を用いた都市間高速道路の交通流のサービスの質の評価 Reviewed

近田博之・中村英樹

高速道路と自動車 Vol. 63 ( 2 ) page： 22 - 29 2020.2

Analysis of Travel Speed on 4-Lane Signalized Arterials Open Access

Akandwanaho E., Nakamura H.

Transportation Research Procedia Vol. 48 page： 890 - 903 2020

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

Open Access

Traffic safety culture of professional drivers in the State of Qatar Open Access

Timmermans C., Alhajyaseen W., Reinolsmann N., Nakamura H., Suzuki K.

IATSS Research Vol. 43 ( 4 ) page： 286 - 296 2019.12

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

Open Access

An Analysis on the Impact of Autonomous Vehicle Mixture on Capacity of Signalized Intersections

Study on Start-up Lost Time at Signalized Intersections Considering Downstream Conditions Reviewed

Zhu, H. and Nakamura, H.

Vol. 75 ( 5 ) page： I_1121 - I_1130 2019.12

Estimation of Roundabout Entry Capacity and Passenger Car Equivalent for Heavy Vehicles Considering the Impact of Geometric Elements Reviewed

Fang, Y., Zhang, X. and Nakamura, H.

Journal of JSCE D3 Vol. 75 ( 5 ) page： I_1167 - I_1176 2019.12

ラウンドアバウト幾何構造の安全性能評価のためのリスク指標モデリング Reviewed

吉岡慶祐・中村英樹・下川澄雄・森田綽之

土木学会論文集D3 Vol. 75 ( 3 ) page： 191 - 201 2019.10

WANIBE Kazuma, KAKIMOTO Yuji, NAKAMURA Hideki, IRYO-ASANO Miho

JSTE Journal of Traffic Engineering Vol. 5 ( 2 ) page： A_167 - A175 2019.2

Language：Japanese Publisher：Japan Society of Traffic Engineers

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.

DOI： 10.14954/jste.5.2_a_167

ESTIMATION OF ROUNDABOUT ENTRY CAPACITY AND PASSENGER CAR EQUIVALENT FOR HEAVY VEHICLES CONSIDERING THE IMPACT OF GEOMETRIC ELEMENTS

Introduction

Tang K.

Global Practices on Road Traffic Signal Control: Fixed-Time Control at Isolated Intersections page： 1 - 5 2019.1

FANG Yao, ZHANG Xin, NAKAMURA Hideki

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 75 ( 5 ) page： I_1167 - I_1176 2019

Language：English Publisher：Japan Society of Civil Engineers

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.

DOI： 10.2208/jscejipm.75.i_1167

MODELING A RISK INDEX FOR EVALUATING THE SAFETY PERFORMANCE OF ROUNDABOUT GEOMETRIC DESIGN

YOSHIOKA Keisuke, NAKAMURA Hideki, SHIMOKAWA Sumio, MORITA Hirohisa

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 75 ( 3 ) page： 191 - 201 2019

Language：Japanese Publisher：Japan Society of Civil Engineers

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.

DOI： 10.2208/jscejipm.75.191

STUDY ON START-UP LOST TIME AT SIGNALIZED INTERSECTIONS CONSIDERING DOWNSTREAM CONDITIONS

ZHU Hong, NAKAMURA Hideki

Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) Vol. 75 ( 5 ) page： I_1121 - I_1130 2019

Language：English Publisher：Japan Society of Civil Engineers

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.

DOI： 10.2208/jscejipm.75.i_1121