Can Left-turn Waiting Areas Improve the Capacity of Left-turn Lanes at Signalized Intersections?

This study estimated the operational impacts of left-turn waiting areas at signalized intersections using the VISSIM simulation technique. A procedure was proposed to model capacity of single left-turn lanes with waiting areas in VISSIM. Using data collected from 7 different sites, the VISSIM simulation model was calibrated and validated. The simulation results of the calibrated VISSIM model were compared to field measured capacity, as well as the capacity estimated using the analytical model developed in our previous studies. The calibrated VISSIM simulation model yields a Mean Absolute Percent Error (MAPE) of 8.28% for the exclusive left-turn lanes, indicating that VISSIM provides reasonable capacity estimates for left-turn lanes with waiting areas at signalized intersections. Based on the calibrated VISSIM simulation model, the capacity for left-turn lanes with waiting areas with different storage capacity was compared with the scenario for which the left-turn waiting area is not installed. The results show that the use of left-turn waiting areas could increase the capacity for the left-turn movement, and the capacity gains would increase with the increase in the size of the left-turn waiting areas.