Abstract

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Title:: Design and optimization of signalized tandemintersections with displaced leftturn

Author(s):: HUA Xue-dong; WANG Bao-jie; YANG Jian-qiang; WANG Wei; ZHAO De; (1. School of Transportation, Southeast University, Nanjing 210096, Jiangsu, China; 2. School of Architecture,Southeast University, Nanjing 210096, Jiangsu, China; 3. School of Highway, Changan University,Xian 710064, Shaanxi, China; 4. Department of Civil and Environmental Engineering,National University of Singapore, Singapore 119077, Singapore)

Keywords:: traffic engineering; traffic design; tandem intersection; displaced leftturn; signal control; operation optimization

Abstract:: To reduce traffic conflicts at left turns (LT) through rightturn movements and increase the intersection capacity, the concept of tandem intersection (TI) was extended with displaced leftturn (TIDLT). By displacing LT lanes, optimizing presignals, and redesigning traffic flow movements, lane utilization could be improved. An optimization model was proposed for the integrated design of lane assignment, the length and number of the displaced LT lanes, and signal control plan. An optimization problem was solved by reducing it into a set of linear programming problems. A numerical test was conducted with four scenarios to show the performance of TIDLT. Besides, a sensitivity analysis was demonstrated to compare TIDLT with TI and conventional intersection(CI) under different LT ratios. The results show that TIDLT can improve the capacity of intersections, the capacity is improved by 60% to 80% and 1% to 3% when compared with that by CI and TI, respectively. TIDLT should be applied to optimize utilization. It is more likely to be the best when the LT ratio is low, while TI is more suitable under high LT ratio conditions. Furthermore, TIDLT is not suitable for intersections that are always undersaturated, as extra capacity is not needed in this case, and the displaced LT can lead to more delay time and safety issues. 3 tabs, 4 figs, 25 refs.