PURPOSES : Even when autonomous vehicles are commercialized, a situation in which autonomous vehicles and regular drivers are mixed will persist for a considerable period of time until the percentage of autonomous vehicles on the road reaches 100%. To prepare for various situations that may occur in mixed traffic, this study aimed to understand the changes in traffic flow according to the percentage of autonomous vehicles in unsignalized intersections. METHODS : We collected road information and constructed a network using the VISSIM traffic simulation program. We then configured various scenarios according to the percentage of autonomous vehicles and traffic volume to understand the changes in the traffic flow in the mixed traffic by scenario. RESULTS : The results of the analysis showed that in all scenarios, the traffic flow on major roads changed negatively with the mix of autonomous vehicles; however, the increase or decrease was small. By contrast, the traffic flow on minor roads changed positively with a mix of autonomous vehicles. CONCLUSIONS : This study is significant because it proactively examines and designs traffic flow changes in congested traffic that may occur when autonomous vehicles are introduced.

PURPOSES : Because a driving simulator typically focuses on analyzing a driver’s driving behavior, it is difficult to analyze the effect on the overall traffic flow. In contrast, traffic simulation can analyze traffic flow, that is, the interaction between vehicles; however, it has limitations in describing a driver’s driving behavior. Therefore, a method for integrating the simulator and traffic simulation was proposed. Information that could be controlled through driving experiments was used, and only the lane-change distance was considered so that a more natural driving behavior could be described in the traffic flow. METHODS : The simulated connection method proposed in this study was implemented under the assumption of specific traffic conditions. The driver’s lane-changing behavior (lane-changing distance, deceleration, and steering wheel) due to the occurrence of road debris was collected through a driving study. The lane-change distance was input as a parameter for the traffic simulation. Driving behavior and safety were compared between the basic traffic simulation setting, in which the driver's driving behavior information was not reflected, and the situation in which the driving simulator and traffic simulation were integrated. RESULTS : The number of conflicts between the traffic simulation default settings (Case 1) and the situation in which the driving simulator and traffic simulation were integrated (Case 2) was determined and compared for each analysis. The analysis revealed that the number of conflicts varied based on the level of service and road alignment of the analysis section. In addition, a statistical analysis was performed to verify the differences between the scenarios. There was a significant difference in the number of conflicts based on the level of service and road alignment. When analyzing a traffic simulation, it is necessary to replicate the driving behavior of the actual driver. CONCLUSIONS : We proposed an integration plan between the driving simulator and traffic simulation. This information can be used as fundamental data for the advancement of simulation integration methods.

도로협곡에서의 수목식재에 따른 보도 내 교통유발 대기오염도 변화를 살펴보기 위해 오픈소스 전산유체역학 코드 FDS(Fire Dynamics Simulator)를 사용하여 수목 투과지수, 식재 위치 및 유형에 따른 영향을 조사하였다. 광범위한 시뮬레이션을 통해 1) 관목층 만으로만 구성된 사례, 2) 관목층과 아교목층으로 구성된 사례 및 3) 관목층과 교목층으로 구성된 사례를 포함하는 400개의 시나리오 사례 중 399개 사례에 대해 유효한 데이터를 생성하였다. 분석결과, 보도 위에서 관찰되는 평균화된 정상상태 대기오염 농도는 식재유 형과는 무관하게 수목식재 후 약 10% 이상 감소하는 것으로 나타났다. 가장 큰 대기오염 감소효과는 관목층만으로 구성된 사례에서 관찰되었는데 대략 45%까지 감소하는 것으로 나타났다. 이러한 감소효과는 차선에서 인도로 대기오염물질을 직접 수송하는 선회류가 관목층에 의해 유리한 방향으로 변형되는 물리적 과정에 기초한다.

PURPOSES : This study aimed to evaluate the influence of weigh-in-motion (WIM)-based overloading enforcement systems on the performance of a traffic stream. METHODS: A VISSIM simulator was used for the evaluation of various scenarios. Actual WIM event data collected from the field was used for simulation parameter calibrations. A genetic algorithm was incorporated into the calibration procedure to identify the optimal set of parameters. The impact of the overloading enforcement systems on the traffic stream was investigated from the perspective of mobility, safety, and environmental compatibility. RESULTS: The existing enforcement system is generally superior to the new pilot enforcement system. CONCLUSIONS : Policies and regulations to fully exploit the benefits of WIM-based enforcement systems on freeways need to be developed and implemented. In addition, various enforcement scenarios should be tested on both actual and simulated environments.

국내 평면교차로 설계지침에서“평면교차로란 도로와 도로가 서로 교차 또는 접속되는 공간 및 그 내 부의 교통시설물을 말하는 것으로 교차로의 기하구조, 운영방법 등에 따라 운전자가 통행노선을 선정하는 의사결정 지점이 된다.”로 정의하였다. 교차로의 운영에 따라 파급효과는 연계 노선 전체의 도로에 중요 한 영향을 미치기 때문에 교차로 설계는 매우 중요한 문제이다. 그러나 현 지침에서는 각 교통운영 방안 별 도로･교통조건을 명확하게 제시하지 않았고“교통량 증가에 따라 순차적으로 시행”한다는 정성적 조 건만 제시하였다. 또한 경찰청의 ʻ국내 교통신호기 설치･관리 매뉴얼(2011)ʼ에서도 국내 도로･교통 여건에 대한 적정성 검토없이 미국 MUTCD(2009)의 기준 1(최소 차량 교통량)과 동일한 기준을 준용하고 있다. 그러나 이러한 미국 기준도 이론적 배경 부족 및 주관적 판단에 결정되기 때문에 지속적으로 문제점 지적 및 개정 필요성을 지속적으로 지적해 왔다. 따라서, 본 연구에서는 현 관련 기준에서 제시한 최소 교통 신 호등 설치 기준(차로수, 주도로/부도로 교통량)에 대해 시뮬레이션(VISSIM, Synchro) 및 현 운영중인 교 차로를 대상으로 적정성 분석 및 최소 기준을 제시하였다. 또한 차로 수 및 주도로/부도로 교통량 조건이 외에 다른 도로･교통조건(교차로 형태(3지교차로, 4지교차로), 교통량 분포 비율, 좌회전 교통량 비율)을 고려하여 교차로 운영효과를 추가로 분석하였다. 이러한 결과를 토대로 교통 신호등 설치 기준에 대한 재 정립 방향을 제시하였다. 시뮬레이션 결과, 국내에서 제시한 교통 신호등 설치 기준 값은 과다하게 설정 된 것으로 나타났으며, 이로 인해 조기에 교통 신호등 설치됨으로써 불필요한 지체 발생 혹은 불필요한 유지관리 비용 발생 등 비경제적으로 교차로가 운영될 가능성이 높은 것으로 나타났다. 또한 현 기준에서 반영하지 못한 교차로 형태(3지교차로와 4지교차로), 방향별 교통량 분포 비율, 좌회전 교통량 비율도 교 차로 운영 방식에 어느 정도 영향을 미치는 것으로 나타났다.

PURPOSES : The aim of this study was to compare the performance of the QUEENSOD method and the gravity model in estimating Origin-Destination (O/D) tables for a large-sized microscopic traffic simulation network. METHODS : In this study, an expressway network was simulated using the microscopic traffic simulation model, VISSIM. The gravity model and QUEENSOD method were used to estimate the O/D pairs between internal and between external zones. RESULTS: After obtaining estimations of the O/D table by using both the gravity model and the QUEENSOD method, the value of the root mean square error (RMSE) for O/D pairs between internal zones were compared. For the gravity model and the QUEENSOD method, the RMSE obtained were 386.0 and 241.2, respectively. The O/D tables estimated using both methods were then entered into the VISSIM networks and calibrated with measured travel time. The resulting estimated travel times were then compared. For the gravity model and the QUEENSOD method, the estimated travel times showed 1.16% and 0.45% deviation from the surveyed travel time, respectively. CONCLUSIONS : In building a large-sized microscopic traffic simulation network, an O/D matrix is essential in order to produce reliable analysis results. When link counts from diverse ITS facilities are available, the QUEENSOD method outperforms the gravity model.

PURPOSES : This study evaluated the feasibility of implementing protected-permissive left-turn (PPLT) signals at three-leg signalized intersections. METHODS: A three-leg signalized intersection with permissive left-turn was first selected. A VISSIM simulation model was constructed using data collected from the test site. The VISSIM network was calibrated by adjusting related parameter values in order to minimize the difference between the simulated and surveyed critical gap. The calibrated network was validated by the number of waiting left-turning vehicles per cycle. Finally, the mobility and safety measures were extracted from simulation runs in which permissive, protected left turns as well as PPLTs were realized based on diverse traffic volume scenarios. RESULTS : The mobility-related measures of effectiveness (MOEs) of the case with PPLT outperformed the other two left-turn treatment scenarios. In particular, the average waiting time per cycle for the left-turn vehicles in the case with PPLT was reduced by 30 s. The safetyrelated MOEs of the case with PPLT were somewhat higher than those in the case with protected left-turns and much higher than those in the case with permissive left-turns. CONCLUSIONS : Based on the mobility- and safety-related MOEs generated from the VISSIM simulation runs, the use of PPLT seems to be feasible at three-leg signalized intersections where the left-turn is permissive and a pedestrian signal exists at the conflicting approach. However, in order to use the PPLT in earnest, it is necessary to revise the road traffic act, traffic signs, and related manuals.