Agent-based pedestrian cell transmission model for evacuation

Tak, Sehyun,Kim, Sunghoon,Yeo, Hwasoo Informa UK (TaylorFrancis) 2018 Transportmetrica. A, Transport Science Vol.14 No.5

<P>Describing dynamics of pedestrian evacuation is a challenging issue. Many related studies have been conducted in both microscopic and macroscopic views. Microscopic approaches focus on detailed movements of individual pedestrians and they are computationally expensive. Macroscopic approaches have less concern in the individuals, but they are lack of flexibility because they treat pedestrians as unthinking elements that cannot choose their destinations or routes. We propose the agent-based pedestrian cell transmission model (A-PCTM) that puts the merits of both microscopic and macroscopic approaches. We modify the original CTM to improve the computational efficiency and embed the concept of agents that make decisions on their destinations and travel directions. The A-PCTM has procedures of adaptive direction-based path finding, and the effect of such procedures is tested by some simulation cases with different geometric settings. The proposed model shows the flexibility in switching the destination and in choosing the travel direction depending on the situation ahead.</P>

A Comparison Analysis of Surrogate Safety Measures with Car-Following Perspectives for Advanced Driver Assistance System

Tak, Sehyun,Kim, Sunghoon,Lee, Donghoun,Yeo, Hwasoo Hindawi Limited 2018 Journal of advanced transportation Vol.2018 No.-

<P>Surrogate Safety Measure (SSM) is one of the most widely used methods for identifying future threats, such as rear-end collision. Various SSMs have been proposed for the application of Advanced Driver Assistance Systems (ADAS), including Forward Collision Warning System (FCWS) and Emergency Braking System (EBS). The existing SSMs have been mainly used for assessing criticality of a certain traffic situation or detecting critical actions, such as severe braking maneuvers and jerking before an accident. The ADAS shows different warning signals or movements from drivers’ driving behaviours depending on the SSM employed in the system, which may lead to low reliability and low satisfaction. In order to explore the characteristics of existing SSMs in terms of human driving behaviours, this study analyzes collision risks estimated by three different SSMs, including Time-To-Collision (TTC), Stopping Headway Distance (SHD), and Deceleration-based Surrogate Safety Measure (DSSM), based on two different car-following theories, such as action point model and asymmetric driving behaviour model. The results show that the estimated collision risks of the TTC and SHD only partially match the pattern of human driving behaviour. Furthermore, the TTC and SHD overestimate the collision risk in deceleration process, particularly when the subject vehicle is faster than its preceding vehicle. On the other hand, the DSSM shows well-matched results to the pattern of the human driving behaviour. It well represents the collision risk even when the preceding vehicle moves faster than the follower one. Moreover, unlike other SSMs, the DSSM shows a balanced performance to estimate the collision risk in both deceleration and acceleration phase. These research findings suggest that the DSSM has a great potential to enhance the driver’s compliance to the ADAS, since it can reflect how the driver perceives the collision risks according to the driving behaviours in the car-following situation.</P>

Development of a Deceleration-Based Surrogate Safety Measure for Rear-End Collision Risk

Sehyun Tak,Sunghoon Kim,Hwasoo Yeo IEEE 2015 IEEE transactions on intelligent transportation sy Vol.16 No.5

<P>A surrogate safety measure can be used for preventing hazardous roadway events by evaluating the potential safety risk by using information on the driving environment gathered from vehicles. In this paper, the deceleration-based surrogate safety measure (DSSM) is proposed as a safety indicator for rear-end collision risk evaluation based on the safety conditions and the decision-making process during human driving. The DSSM shows how drivers deal with collision risk differently in acceleration and deceleration phases. The proposed surrogate safety model has been validated for severe deceleration behavior, which is a driver-critical behavior in high-risk situations of collision based on microscopic vehicle trajectory data. The results indicate that there is a strong relationship between the proposed surrogate safety measures and crash potential. The measure could be used for collision warning and collision avoidance systems. It has a merit in that it reflects the characteristics of both vehicle (e.g., mechanical braking capability) and driver (e.g., preference for certain acceleration rates).</P>

A Study on Impact of SPAD and Signal Failure Events on Railway Safety Based on Incorporating Train Drivers’ Behaviors into Train-Simulator

Sehyun Tak,Donghoun Lee,Hwasoo Yeo 한국철도학회 2017 International Journal of Railway Vol.10 No.2

The human factor in the current railway system is a dominant cause of collision accidents. There exists a degree of uncertainty to the train driver on the timing of decision-making. Mitigating collision risks that are associated with the uncertainty of driving behavior is a challenging task. In this paper, we propose a train-simulator that incorporates the uncertainty of human driving behavior and its potential collision risk in the current train operation environment. The proposed simulator shows the impacts of driver behavioral errors on the safety performance and evaluates the collision risks associated with the various ranges of behavioral errors when a driver faces unsafe situations such as Signal Passed At Danger (SPAD) and signal failure events. The findings of this study reveal that there is a strong relationship between the number of taking evasive actions and the range of driving behavioral errors. This implies that the proposed train-simulator has a considerable effect in measuring the potential collision risks compared with the existing driving principles without the behavioral error consideration.

Comparison of Various Spacing Policies for Longitudinal Control of Automated Vehicles

Tak, Sehyun,Park, Sungjin,Yeo, Hwasoo U.S. National Research Council, Transportation Res 2016 Transportation Research Record Vol.2561 No.-

Data-Driven Imputation Method for Traffic Data in Sectional Units of Road Links

Tak, Sehyun,Woo, Soomin,Yeo, Hwasoo IEEE 2016 IEEE transactions on intelligent transportation sy Vol.17 No.6

<P>Missing data imputation is a critical step in data processing for intelligent transportation systems. This paper proposes a data-driven imputation method for sections of road based on their spatial and temporal correlation using a modified k-nearest neighbor method. This computing-distributable imputation method is different from the conventional algorithms in the fact that it attempts to impute missing data of a section with multiple sensors that have correlation to each other, at once. This increases computational efficiency greatly compared with other methods, whose imputation subject is individual sensors. In addition, the geometrical property of each section is conserved; in other words, the continuation of traffic properties that each sensor captures is conserved, therefore increasing accuracy of imputation. This paper shows results and analysis of comparison of the proposed method to others such as nearest historical data and expectation maximization by varying missing data type, missing ratio, traffic state, and day type. The results show that the proposed algorithm achieves better performance in almost all of the missing types, missing ratios, day types, and traffic states. When themissing data type cannot be identified or various missing types aremixed, the proposed algorithm shows accurate and stable imputation performance.</P>

Real-Time Associative Memory-Based Rear-End Collision Warning System

Lee, Donghoun,Tak, Sehyun,Park, Sungjin,Yeo, Hwasoo SAGE Publications 2017 TRANSPORTATION RESEARCH RECORD Vol.2621 No.-

거리 센서 시스템의 교차로 충돌 방어 성능 평가

김정윤(KIM, Jeongyun),탁세현(Tak, Sehyun),김예은(KIM, Yeeun),여화수(Yeo, Hwasoo) 대한교통학회 2017 대한교통학회 학술대회지 Vol.76 No.-

교차로는 차량과 보행자, 신호와 도로 구성 등의 복합적인 이유로 빈번히 충돌사고가 발생하는 장소다. 교차로에서의 충돌을 방지하기 위한 예방형 제어 시스템을 개발하고자, 우선적으로 거리 센서기반 사고 방어 시스템의 교차로 사고에서의 효용을 분석하였다. 단계적 고속도로 리서치 프로그램 Second Strategic Highway Research Program(SHRP2) 일상주행연구 naturalistic driving study(NDS)에서 수집된 사고/준사고 상황에서의 거리 측정 데이터를 기반으로 분석하였고 총 130건의 차량과 차량 간 사고를 분석하였다. 사고 데이터를 기반으로 거리 센서의 사고 방지 성능을 도출하기 위해 먼저, 센서가 사고 물체 탐지 시각과 운전자가 사고 인지 후 반응한 시각을 비교하는 시간 기준 분석을 하였고, 그 다음으로 센서가 사고 물체를 탐지한 시각에서의 차량 속도 데이터와 사고차량 간의 거리 데이터를 기준으로 사고를 방지할 수 있는 지를 함께 분석하였다. 이를 통해 거리 센서의 교차로 사고 방어율을 도출하고, 방어가 가능한 사고 종류를 분석하였으며, 평가 결과 차량간 사고 15개 중 각 8개의 사나리오를 방어할 수 있는 반면, 각 7개의 시나리오에 대해서는 데이터가 부족하거나 취약한 성능을 보였다. 이것은 거리 센서의 시야각이 좁은 이유로 나타난 한계점으로, 추가적인 센서 설치를 통해 시야각을 넓히거나 다른 시스템과의 통합을 통해 보완이 필요할 것으로 보인다.

안전성과 모니터링지표 기반의 실시간 철도안전 감시제어 시스템의 프레임워크에 대한 개념 연구

이동훈(Donghoun Lee),탁세현(Sehyun Tak),김상암(Sangahm Kim),여화수(Hwasoo Yeo) 한국철도학회 2016 한국철도학회논문집 Vol.19 No.4

교통소외지역 자율주행 모빌리티 서비스를 위한 도로 환경 분석 : 대구광역시와 세종특별자치시를 중심으로

김아름,우보람,탁세현,임서현,Kim, Ahreum,Woo, Boram,Tak, Sehyun,Lim, Seohyun 한국ITS학회 2022 한국ITS학회논문지 Vol.21 No.5

The introduction of Connected and Automated(CAD) technology has a growing interests especially in areas with low demand for transport, where often the local transport services do not connect to peripheral areas for more efficient and convenient mobility services. However, there are few researches on CAD-based mobility services in areas with low demand for transport. Because current researches are mainly focuses on introduction of CAD-based mobility services in area with high demand for transport such as urban and highway. These two areas have different road environments and these differences require different driving technology especially related to Operational Design Domain(ODD). ODD is important factors for introduction of CAD-based mobility services. Therefore, we compare the road environments of areas with low demand for transport and areas with high demand for transport in terms of ODD. In addition, this paper proposes suggest guidance for the introduction of CAD-based mobility services in areas with low demand for transport such as rural and suburban areas.