Multiobjective Evaluation of Left-Turn Waiting Areas at Signalized Intersections in China

This study presents a procedure for evaluating the impacts of left-turn waiting areas at signalized intersections considering multiple performance measures, including traffic operations, safety, environmental impacts, and fuel consumption. Data were collected at 33 sites in Nanjing, China. Vissim simulation models were developed for both isolated intersections and a roadway segment to evaluate the operational and environmental impacts of left-turn waiting areas at signalized intersections. The frequency of traffic conflicts associated with the left-turning traffic was considered the safety performance measure. The life-cycle cost method was used to combine different components in the total benefit for an isolated intersection. It was found that first, for an isolated signalized intersection, the implementation of left-turn waiting areas is overall economically beneficial when the storage capacity of the left-turn waiting area is more than one vehicle. Second, when signal coordination at arterials is considered, a set of factors may determine the overall benefits of using left-turn waiting areas, including the distance between adjacent intersections, the signal timing strategy, the size of left-turn waiting areas, and other factors. The overall benefits of using left-turn waiting areas should be determined case by case. For more than 70% of the randomly generated network cases, the lead-lag phase yields greater maximized progression bandwidth than the dual lagging phase. In this situation, it is generally recommended to implement a left-turn waiting area on one approach with a lead-lag left-turn phase. For only a few network cases in which the maximized progression bandwidth of the lag-lag phase is larger than that of the lead-lag phase, the implementation of left-turn waiting areas on both approaches with a dual-lagging left-turn phase is recommended.