PURPOSES : This study evaluates the effectiveness of traffic flow optimization when giving safety strategy guidance to a connected autonomous vehicle (CAV) based on information received through infrastructure cooperation in a V2X environment for non-signal intersection. METHODS : To evaluate the effectiveness of safety strategy guidance based on developed traffic flow control algorithm at a non-signalized intersection, it was implemented on simulation. A scenario based on the Level of Service (LOS) and the market penetration rate(MPR) of autonomous vehicles was established. The simulation results were divided into safety, operation, and environment to evaluate the effect, and the effect of optimizing traffic flow was finally derived through the integrated evaluation score. RESULTS : As a result, when safety strategy guidance was provided, the number of conflicts and CO emissions decreased by about 29% and about 15%, improving safety and environmental performance. In the case of operation, the mean of delay time was increased overall by 1%, but in the case of MPR 50 and above, the delay time was reduced by about 38%, thereby increasing operation. Finally, the aspect of traffic flow optimization, effectiveness of safety strategy guidance was derived through the integrated evaluation score, and the average integrated evaluation score improved from MPR 20 or higher. CONCLUSIONS : Providing guidance had the effect of optimizing traffic flow at a non-signal intersection. In the future, V2X communications will provide CAV with algorithm-based guidance developed in this study to control driving behavior. it will support safe and efficient driving at non-signal intersections.

PURPOSES : This study tries to develop the accident models of 4-legged signalized intersections in Busan Metropolitan city with random parameter in count model to understanding the factors mainly influencing on accident frequencies. METHODS: To develop the traffic accidents modeling, this study uses RP(random parameter) negative binomial model which enables to take account of heterogeneity in data. By using RP model, each intersection’s specific geometry characteristics were considered. RESULTS : By comparing the both FP(fixed parameter) and RP modeling, it was confirmed the RP model has a little higher explanation power than the FP model. Out of 17 statistically significant variables, 4 variables including traffic volumes on minor roads, pedestrian crossing on major roads, and distance of pedestrian crossing on major/minor roads are derived as having random parameters. In addition, the marginal effect and elasticity of variables are analyzed to understand the variables’impact on the likelihood of accident occurrences. CONCLUSIONS :This study shows that the uses of RP is better fitted to the accident data since each observations’specific characteristics could be considered. Thus, the methods which could consider the heterogeneity of data is recommended to analyze the relationship between accidents and affecting factors(for example, traffic safety facilities or geometrics in signalized 4-legged intersections).

PURPOSES : The purpose of this study is to present a linear programing optimization model for the design of lane-based lane-uses and signal timings for an isolated intersection. METHODS: For the optimization model, a set of constraints for lane-uses and signal settings are identified to ensure feasibility and safety of traffic flow. Three types of objective functions are introduced for optimizing lane-uses and signal operation, including 1) flow ratio minimization of a dual-ring signal control system, 2) cycle length minimization, and 3) capacity maximization. RESULTS : The three types of model were evaluated in terms of minimizing delay time. From the experimental results, the flow ratio minimization model proved to be more effective in reducing delay time than cycle length minimization and capacity maximization models and provided reasonable cycle lengths located between those of other two models. CONCLUSIONS : It was concluded that the flow ratio minimization objective function is the proper one to implement for lane-uses and signal settings optimization to reduce delay time for signalized intersections.

PURPOSES : Before-and-after studies of red light cameras were conducted with the aim of reducing the number of side right-angle collisions. Three different methods were used for the before-and-after studies, and the analysis results were compared. METHODS: This research used the naive before-and-after method, the comparison-group method, and the empirical Bayes method to study the effects of red light cameras on side-angle collisions. The results of the three before-and-after methods were compared and interpreted in terms of safety indications at signalized intersections. RESULTS: The research results showed that side right-angle collisions can be reduced by installing red light cameras at signalized intersections. All three methods guarantee safety improvements of 25~30% on average. With regard to the results of each method, the naive before-and-after method, the comparison-group method, and the empirical Bayes method showed safety improvements of 25.6%, 27.8%, and 29.7%, respectively. CONCLUSIONS: It was concluded that red light cameras are an effective countermeasure to improve intersection safety. In particular, by installing red light cameras, side right-angle collisions can be reduced by up to approximately 25~30%.

PURPOSES : The purpose of this study is to propose delay-minimizing operation methodology of a signalized intersection based upon optimization of lane-uses on approaching lanes for an intersection. METHODS: For the optimization model of lane-uses, a set of constraints are set up to ensure feasibility and safety of the lane-uses, traffic flow, and signal settings. Minimization of demand to saturation flow ratio of a dual-ring signal control system is introduced to the objective function for delay minimization and effective signal operation. Using the optimized lane-uses, signal timings are optimized by delay-based model of TRANSYT-7F. RESULTS : It was found that the proposed objective function is great relation with delay time for an intersection. From the experimental results, the method was approved to be effective in reducing delay time. Especially, cases for two left-turn lanes reduced greater delays than those for a left turn lane. It is noticed that the cases for different traffic volume by approach reduced greater delays than those for the same traffic volume by approach. CONCLUSIONS : It was concluded that the objective function is proper for lane-uses optimizing model and the operation method is effective in reducing delay time for signalized intersections.

신호교차로 구간의 위험원인에 대해서 사전에 사고예방을 강구한다면 사고건수를 줄이는데 도움이 될 것이다. 특히, 신호교차로에서 기하구조 개선과 같이 많은 예산을 투자하지 않더라도 사고감소효과를 낼 수 있다. PG(Positive Guidance) 기법은 신호교차로에서 도로안전시설물의 개선을 통하여 교통사고를 예방할 수 있다. 본 연구에서는 과속으로 인해서 사고위험성이 높은 신호교차로 1곳을 선정하여 대상지점의 문제점 분석 및 개선방안을 도출하였다. 선정된 구간은 시뮬레이터를 활용하여 대상구간의 현황을 그대로 재현하여 실험하였다. 이를 토대로 PG개선 전 후의 지점별 속도효과가 있는지를 검증하기 위해서 t 검증을 실시하였다. 그 결과, 개선 후에는 운전자가 정보를 충분히 제공받아서 신호교차로 부근에서 속도를 감속하는 것으로 나타났다. 향후 본 연구를 토대로, PG기법을 활용할 수 있는 일부 신호교차로에 대해서 많은 비용을 투자하지 않더라도 저비용으로 교통사고 감소 효과를 거둘 수 있다.

이 연구는 고령운전자의 사고를 다루고 있다. 본 논문은 고령운전자와 일반운전자 사이의 교통사고 특성을 비교 분석하고, 사고모형을 개발하는데 목적이 있다. 이를 위해 본 연구에서는 청주시 4지 신호교차로를 중심으로 두 운전자 집단 간의 차이를 검증하고, 포아송 및 음이항 회귀모형을 개발하는데 중점을 두고 있다. 분석된 주요 연구결과는 다음과 같다. 첫째, 고령운전자와 일반운전자 사고의 차이점이 시간대별, 사고유형별 등으로 파악되었다. 둘째, 통계적으로 설명력이 높은 고령 및 일반운전자 총 3개의 사고모형이 개발되었다. 마지막으로 공통변수와 특정변수를 활용하여 고령 일반 운전자 사고모형의 차이가 비교 분석되었다.

신호교차로는 도로조건, 교통조건, 신호조건 능 방대한 입력자료를 바탕으로 용량분석을 시행하고 이 과정을 토대로 주요 효과척도인 지체를 산정하여 신호교차로의 서비스 수준을 판단한다. 하지만 이러한 용량 및 서비스 수준 결정에 있어 바탕이 되는 현장 데이터(회전 교통량, 도로의 기하구조, 신호시간, 접근로 구배, 중차량비, 첨두시간계수, 차량도착형태 등) 입력자료의 불확실성으로 인해 초래되는 결과의 오류에 대해서는 고려되지 않고 있는 실정이다. 이로 인해 추정된 용량 및 서비스수준에 대한 신뢰성을 검증할 수 없는 문제를 내포하고 있다. 따라서 본 연구에서는 해당 교차로 접근로의 교통량과 중차량 비율 및 도로의 기하구조 등 입력자료의 불확실성이 용량해석과 서비스수준 결정에 끼치는 영향을 고려해보고 이틀에 의한 영향을 최소화할 수 있는 방안을 제시하고자 한다.

This study was focused on analyzing the headway of various types of trailer in Pusan city with the high heavy vehicle rate. Then Passenger Car Equivalent(PCE) was calibrated in order to identify the impact of trailers in the traffic flow at the signalized intersections. To fulfill this goal types of trailer were classified into five categories such as full trailer semi-trailer unloaded semi-trailer semi-trailer loaded with 20ft container and semi-trailer loaded with 40ft container and Passenger Car Equivalents were identified. the Results are as follows: 1) The PCE’s were 2.64, 1.51, 2.09, 2.16 and 2.23 respectively. 2) The saturation flow rate on the signalized intersection was lower than that on the multi-lane highway in the big city of Korea. 3) The start-up delay on the thru lane was similar to the average value in our country but the start-up delay on the left-turn lane was longer than the average value in our country by the impact of container Vehicles.