Institute of Transportation, MOTC

　　Traffic jams are a big issue in most cities. The traffic jam causes energy waste and air pollution. Arterials in some urban areas are often oversaturated in peak hours. Oversaturated conditions include spillback, lane blockage, and unbalance queue which is caused by different turning ratio and will increase lane-changing behavior. However, land acquisition for road construction becomes more and more difficult. Retiming traffic signals is an efficient and low-cost way to reduce road congestion. This study proposes a model which optimizes signal timings under oversaturated conditions. The optimized signal timings from TRANSYT-7F, TRANSYT 14, and the proposed model input into TSIS for comparison. The result presents the proposed model reduces total delay or increases total throughput under oversaturated conditions as well as near-oversaturated conditions.