A Traffic Control Strategy for Congested Exit-Ramp Area in Urban Freeway

Traffic control strategy for heavily congested exit ramps in urban freeway, especially for Ring-Road in Seoul, is presented in this paper. A new concept of traffic signal control was prepared fur the traffic signals engaged in the exit ramp and the immediate area. Traffic signal control methodology far oversaturated traffic conditions such as equity offset and imbalanced splits were applied. The exit ramps suffering from serious traffic congestion were selected for the test of the proposed control strategy. After simulation trials, it was found that the control strategy was effective in preventing main-line queue spill-back, and managing queue lengths between the exit traffic and the adjacent street traffic. Field test was conducted at Hongeun exit ramp. The traffic congestion at the Hongeun exit ramp was significantly relieved due to the exit ramp control.