Evaluating the Operational Impacts of Left-Turn Waiting Areas at Dual Left-Turn Lanes at Signalized Intersections

Abstract

In recent years, left-turn waiting areas were increasingly used to improve traffic efficiency at signalized intersections in China. This paper evaluated the operational impacts of left-turn waiting areas at dual left-turn lanes at signalized intersections. An analytical model was proposed to estimate the capacity of dual left-turn lanes with waiting areas. Based on the data collected at 12 sites in Nanjing, cross-sectional analysis were conducted to compare the start-up lost time and saturation headways of left-turn passenger cars under four scenarios. The results indicated that outside left-turn lanes provide slightly lower. For both the inside and outside left-turn lanes, the use of left-turn waiting areas did not significantly affect the saturation headways of left-turn passenger cars behind the stop bar. It was found that left-turn waiting areas increased capacity of dual left-turn lanes and the capacity gains would increase with the increase in the size of the left-turn waiting areas.