Soon-Yong Park

Evaluation of Multi-legged Roundabout Using Surveyed Critical Gap Acceptance

In this paper, considering the characteristics of the driver at roundabouts by investigating the critical gap acceptance on various traffic conditions, multi-legged roundabouts were evaluated. The gap acceptance and rejection of 4-legged, 5-legged, 6-legged, and 7-legged roundabout were surveyed on real fields, and the critical gap acceptance was estimated using Raff`s methods. Derived the critical gap acceptance was processed calibration and validation for micro-simulation, and then multi-legged roundabouts under variable conditions such as variations of traffic volume, turning ratio, and size of inscribed circle diameter were evaluated to verify operating conditions of roundabouts. As the results, according to the operating traffic volume and turning ratio, the inscribed circle diameters were proposed at each level of service. These inscribed circle diameters were able to reflect the guideline of geometric design for multi-legged roundabouts.

Evaluation of Drivers` Detection Distance according to the Local Lightings Condition of Crosswalk Illumination

This study analyzes evaluation of drivers’ detection distance according to the local lightings condition of crosswalk illumination whichcan be installed with or without the continuous lightings; here, continuous lightings mean the lightings installed with a regular spac-ing along the roadside of two lanes and four lanes. The study facilities dummy-detection-distance as a measure of effects observedaccording to the varying lighting conditions; day-time, night-time with continuous lightings only, night-time with the combination ofcontinuous lightings and crosswalk lightings, night-time without lightings at all, and night-time with crosswalk lightings only. Adummy was installed to mimic the school-age-child who are 110 cm tall about to cross the road at crosswalk. Field test was carriedout at two places; one is four lanes operated roads with the continuous lightings and the other is two lanes operated roads without thecontinuous. The corresponding limited speeds are 70 and 60 kph, respectively. With the data of 15th percentile dummy-detection-dis-tance for four lanes operated roads, we conclude the distance for continuous lightings only was not satisfying the Stopping Sight Dis-tance required at 70 kph design speed. The distance was increased with the order of combination of continuous lightings andcrosswalk lightings, day-time condition, and continuous lightings only. With the same data analysis for two lanes operated roads, weconclude the distance for day-time condition only satisfy the Stopping Sight Distance required at 60 kph design speed. Especially, theaverage, 85% tile, 50% tile, 15% tile of a no-night-time lighting (street lamps off) were determined that the subject detection distancewas very shorter than Stopping Sight Distance. Therefore, this insufficient sight distance could make heighten the possibility of accident.Key words : Road Safety, Street Lightings, Crosswalk, Visibility Distance, Stopping Sight Distance

Developing and Evaluation of Coordinated Semi - Actuated Signal Control for Field Application

본 연구에서는 지방부 간선 또는 지선 축에서 효과적으로 사용 가능한 연동형 반감응 신호제어 알고리즘을 개발하고 이를 평가하였다. 연동형 반감응 신호제어에 대한 모의실험 결과를 살펴보면, 주?부 도로의 교통량 차이가 커질수록 연동형 반감응 신호제어의 지체가 최적화된 고정식 신호제어에 비해 감소하는 것을 확인하였다. 그러나 주부도로의 교통량이 같거나 전체 교통량이 많아지면 최적화된 고정식 신호제어의 지체가 더 낮게 나타났으며, 횡단 보행량이 많아질수록 차량 지체가 증가하는 것으로 확인되었다. 따라서 연동형 반감응 신호제어는 차량 교통량이 일정수준 이하인 곳에 적용하되, 횡단 보행량을 고려하여 적용지역을 선별해야 할 것이다.