研究者詳細 - 中村　英樹

実証実験による瓢箪型ラウンドアバウト幾何構造の検討

奥城洋, 吉岡慶祐, 石黒雄紀, 中根武志, 松岡寿章, 首藤貴子, 張馨, 中村英樹, 阿部義典, 神戸信人, 下川澄雄

交通工学論文集 8 巻 ( 4 ) 頁： B_18 - B_25 2022年4月

記述言語：日本語出版者・発行元：一般社団法人交通工学研究会

愛知県豊橋市牧野町における県道と市道の 4 枝無信号交差点は，総流入交通量が約 15,000 台/日と比較的多いが無信号で運用されている．そして，市道が鋭角の食い違い交差となっていることなど，交通安全上の課題を抱えている．その対策案として，瓢箪型ラウンドアバウトの導入が計画されているものの，国内では市街地における導入事例がなく，また，ラウンドアバウトマニュアルにおいても正円でないラウンドアバウトの幾何構造に関する設計の考え方などは記載がない状況である．そこで本研究では，実験フィールドに実物大の仮設ラウンドアバウトを設置し，実証実験を通して瓢箪型ラウンドアバウトの形状を検討した．本稿では，各種実験の概要と分析結果，および望ましいラウンドアバウト形状の検討結果について報告する．

DOI： 10.14954/jste.8.4_b_18

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

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

INTERNATIONAL JOURNAL OF INTELLIGENT TRANSPORTATION SYSTEMS RESEARCH 20 巻 ( 1 ) 頁： 103 - 116 2022年4月

記述言語：日本語出版者・発行元：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 46 巻 ( 1 ) 頁： 26 - 35 2022年4月

出版者・発行元：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 46 巻 ( 1 ) 頁： 14 - 25 2022年4月

出版者・発行元：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 46 巻 ( 1 ) 頁： 1 - 2 2022年4月

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

IATSS Research 46 巻 ( 1 ) 頁： 63 - 72 2022年4月

出版者・発行元：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 46 巻 ( 1 ) 頁： 73 - 81 2022年4月

出版者・発行元：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 46 巻 ( 1 ) 頁： 36 - 45 2022年4月

出版者・発行元：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 14 巻 ( 0 ) 頁： 1958 - 1975 2022年3月

記述言語：英語出版者・発行元：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 14 巻 ( 0 ) 頁： 1870 - 1887 2022年3月

記述言語：英語出版者・発行元：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

道路構造・交通運用と交通量変動を考慮した日交通量-速度関係のモデル化査読有り

柿元祐史, 中村英樹

交通工学論文集 8 巻 ( 2 ) 頁： A_62 - A_72 2022年2月

記述言語：日本語出版者・発行元：一般社団法人交通工学研究会

道路事業評価は、種級区分や車線数などに応じて一律に決まる日単位の交通量-速度関係(Q-V)を用いて費用便益分析を行っている。しかし、既往の Q-V では実際の道路交通条件を十分正確に反映できないことや、地域の交通量の変動を十分に考慮できてないことなど、その設定方法に根本的な課題が残されている。本研究では、道路構造・交通運用を考慮した時間交通量-速度関係(q-v)と交通量変動指標を用いて、Q-V のモデル化を行った。実観測データの交通量変動と q-v から各時間帯の時間平均旅行速度を算出し、重み付き調和平均をとることにより、ある日交通量時の日平均旅行速度を算出し、Q-V を設定した。この Q-V は、ピーク率と昼夜率の値によってその形状を説明でき、構築したモデルにより実際の道路・交通条件を考慮した Q-V の推定が可能となった。

DOI： 10.14954/jste.8.2_a_62

ラウンドアバウト幾何構造要素と車両走行位置の関係分析

西垣裕樹, 張馨, 柿元祐史, 中村英樹

交通工学論文集 8 巻 ( 2 ) 頁： A_15 - A_21 2022年2月

記述言語：日本語出版者・発行元：一般社団法人交通工学研究会

日本各地において、様々な幾何構造のラウンドアバウト(RAB)が導入されており、今後さらに普及が進んでいくと考えられる。しかし、設計時の想定と実際の走行位置が異なることで、中央島などの構造物への接触や、小型車であるにも関わらずエプロン上を走行するといった事例が散見される。車両の走行位置には、RAB の中央島直径や隅角部形状といった様々な幾何構造要素の組み合わせが大きく影響するが、その関連性は未だ十分明らかとなっていない。そこで本研究では、日本の RAB を対象に、幾何構造要素の違いが走行位置に与える影響を明らかにすることを目的とする。分析結果から、エプロン幅員や環道幅員が走行位置に大きな影響を与えることが確認された。また、走行位置分布の推定モデルを用いることで、設計段階において走行位置を予測することが可能となった。

DOI： 10.14954/jste.8.2_a_15

道路利用特性指標を用いた道路ネットワークの階層化度の提案

関原敏裕, 柿元祐史, 中村英樹, 井料美帆, 張馨

交通工学研究発表会論文集 42 巻 ( 0 ) 頁： 455 - 462 2022年

記述言語：日本語出版者・発行元：一般社団法人交通工学研究会

道路ネットワークが概成したわが国において、依然として発生している道路交通問題の解決策の一つとして、機能階層型道路ネットワークの考え方が重要である。本研究では、道路ネットワークがどの程度機能階層的に利用しうるかを評価する方法について提案する。3つの階層を設定した仮想道路ネットワークにおいて、自由走行時を対象とした最短経路探索を行い、トリップ長と階層利用に関する道路利用特性指標を算出する。この指標値から想定される道路ネットワークの状態から、その機能階層性を4段階の階層化度で評価する方法を提案した。そして、岐阜南部と静岡西部の道路ネットワークを対象としてケーススタディを行った。その結果、現状では機能階層性に関する評価は低く、これを向上するためには、中位階層の道路が必要であることが明らかとなった。

DOI： 10.14954/jsteproceeding.42.0_455

道路ネットワークの機能階層性と道路条件との関連分析

富永真弘, 柿元祐史, 中村英樹, 関原敏裕

交通工学研究発表会論文集 42 巻 ( 0 ) 頁： 463 - 469 2022年

記述言語：日本語出版者・発行元：一般社団法人交通工学研究会

これまでの堅実な整備により日本の道路ネットワークは概成しつつあるが、道路ネットワークを構成する各道路の交通機能の性能の考慮が必ずしも十分でなく、幹線道路での低い旅行速度や生活道路での抜け道利用といった問題が残存している。このため、各道路が目指すべき交通機能に応じて階層的に利用されているかといった機能階層性の観点から、道路ネットワークを見直す必要がある。そこで本研究は、道路計画設計の専門家に対するアンケート調査によって、機能階層性に影響を与える要因を明らかにすることを目的とする。調査の結果、機能階層性にはトリップ長、旅行速度に関する条件が相互に影響することを確認し、それらの組合せによって機能階層性を評価する必要性を明らかにした。

DOI： 10.14954/jsteproceeding.42.0_463

ドライバー認識と不安全行動の関連分析

加古陽子, 柿元祐史, 朱宏, 中村英樹

土木学会論文集D3（土木計画学） 77 巻 ( 5 ) 頁： I_915 - I_924 2022年

記述言語：日本語出版者・発行元：公益社団法人土木学会

近年，日本の年間交通事故死者数は減少傾向にある．今後，交通事故を一層減らすためには，交通事故につながる交通違反・危険運転などの不安全行動とそれに対するドライバーの認識との関係を正しく理解し，効果的な取締り・交通安全政策を実施していく必要がある．そこで本研究では，各種不安全行動に対するドライバーの認識の関連を定量的に示すことを目的とする．日本のドライバーに対するアンケート調査データを用いて構造方程式モデリングを行った結果，ドライバー認識が行動の決定に与える影響の大きさは，年齢層が若いほど不安全行動を肯定する態度と運転技能への自信の影響が大きく，容認による影響は小さいことがわかった．この年齢層による影響の差は，飲酒運転と漫然運転で顕著に見られ，速度超過運転ではその差は小さいことがわかった．

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 8 巻 2022年

出版者・発行元：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 163 巻頁： 106468 2021年12月

記述言語：英語出版者・発行元：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 159 巻頁： 106288 2021年9月

記述言語：英語出版者・発行元：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