PURPOSES : Basic research to calculate the appropriate gap acceptance for autonomous vehicles at merging section. Research on whether users prefer short or long gap acceptance. METHODS : Using a driving simulator, experience autonomous driving with different gap acceptance in different weather condition, and analyze which gap acceptance is preferred using survey and biometric data. RESULTS : Regardless of the weather condition, long gap acceptance was preferred, and difference was especially clear in rainy or foggy situation. CONCLUSIONS : It was analyzed that users prefer long gap acceptance over short gap acceptance, and that they feel less frustrated due to long gap acceptance when weather condition is poor.

PURPOSES: A hard shoulder lane (HSL) is a method of solving severe traffic congestion on an expressway. Recently, it has been applied to several expressways in Korea, and there have been numerous positive effects, which include increasing the road capacity and reducing traffic congestion. However, these effects have been limited due to tunnels which created a‘ bottle-neck’effect in HSL application for longer road segments. In the tunnel sections, an HSL is generally not operational owing to problems such as narrow roads and the risk of accidents. If an HSL can be extended to tunnel segments, great positive effects can be achieved. Therefore, this study was conducted to evaluate driver behavior and stability to investigate the risk of HSL in tunnels. METHODS: The Driving Simulator experiments were conducted using some scenarios for the Geumnam and Seojong tunnels on the Seoul- Chuncheon Highway. Based on data from the experiments such as running speed, lateral replacement, and steering handling, the running stabilities of participants were analyzed. In addition, traffic flow data from VDS(Vehicle Detection System) were analyzed as before-after studies. RESULTS: Although there were some differences in driving behaviors, most participants showed safe driving behavior at a speed of less than 50 km/h. CONCLUSIONS : Based on driving behaviors and traffic flow analyses, it is concluded that HSL in tunnels can be an alternative to increase efficiency based on safe driving environments for speeds of below 50 km/h.

PURPOSES :A complete signal system is not always the best solution for improving traffic operation efficiency at intersections. An alternative solution is to use a Protected Permitted Left Turn (PPLT) operation method. However, the PPLT method needs to be developed after a detailed study of driving tendencies, most notably the gap acceptance behavior, for successful implementation. In this study, the gap acceptance behavior was investigated under various variables and weather conditions, especially under rain, and the results were compared to the case of normal weather. The results of this study will be helpful in introducing the PPLT method, and are important considering the tendency of attempting unprotected left turns that is extremely common in Korean drivers.METHODS :Data was obtained by analyzing traffic footage at four intersections on a day when the precipitation was greater than 5 mm/h. The collected data was classified into seven variables for statistical analysis. Finally, we used logistic regression analysis to develop a probability distribution model.RESULTS :Gap, traffic volume, and the number of conflicting lanes were factors affecting the gap acceptance behavior of unprotected left turns under rainy conditions.CONCLUSIONS :The probability of attempting unprotected left turns is higher for larger gaps. On the other hand, the probability of attempting unprotected left turns decreases with an increase in the traffic volume. Finally, an increase in the number of conflict lanes leads to a decrease in the probability of attempting unprotected left turns.

PURPOSES : Permitted left turn is a turning maneuver in which a vehicle turns left using a gap between oncoming vehicles, called gap acceptance, and it enables for more efficient traffic operation at intersections. In Korea, the permitted left turn has not been a common maneuver at signalized or un-signalized intersections. However, many experts and the Police Agency tried to apply this effective turning maneuver at intersections in Korea since 2010. Though the investigation of gap acceptance is significantly important in understanding a driver’s behavior at intersections, there have not been many studies about this topic, specifically a study to develop probability models of gap acceptance behavior. METHODS: In this study, the probability model of gap acceptance behavior for a permitted left turn was developed based on observational field studies. To develop the model, seven variables were analyzed including gap, waiting time, traffic volume, conflict-flow vehicle type, leftturning vehicle type, the number of lane, and time. RESULTS: In the final model, gap and left-turning vehicle type were found to be significant influencing factors. CONCLUSIONS: Through this model development, it was concluded that as the gap size increased, the probability of gap acceptance was higher. Moreover, when a left-turning vehicle was a passenger car, the probability of gap acceptance was higher than compared to large size buses or freight cars.

교통사고 잦은 곳 개선사업은 2010년까지 사업대상지점만을 선정하여 개선사업을 진행하였지만, 2011 년부터 지점뿐만 아니라 구간을 선정하여 개선사업을 추진하고 있다. 그러나 현재까지 사업대상구간을 선 정하는 방법이 명확하지 않은 문제가 있어 사업대상구간 선정 시 혼란이 가중되고 있는 실정이다. 또한 지방부 도로와 같이 교차로가 많지 않은 구간의 사업대상구간 선정은 비교적 수월하지만, 도시부 도로의 교차로가 많은 구간에서는 정량적인 기준을 통해 어떤 구간을 어떻게 선정하여야 하는지 명확한 기준이 없다. 따라서 본 연구에서는 교차로가 많은 특성을 가지고 있는 도시부 도로에서의 사고 잦은 곳 사업대 상구간을 정량적으로 선정할 수 있도록 방법론을 개발하였다. 교통사고 DB는 도로교통공단 교통사고분석시스템(TAAS)을 통해 2012년 발생한 사고 DB를 수집하였 다. 대상구간은 서울시 동작구, 경기도 안양시, 전주시 완산구 13개 축을 선정하여 교통사고 건수 및 심각 도를 분석하였다. 이를 통해 교통사고 잦은 구간을 선정하는 2가지 대안을 제시하였고, 대표성, 구간 선 정 편리성, 범용성, 시스템 적용성 측면에서 대안별 장단점을 분석하여, 최적안을 도출하였다.