Impact Analysis of Start-Up Lost Time at Major Intersections on Sathorn Road Using a Synchro Optimization and a Microscopic SUMO Traffic Simulation

Abstract

Start-up lost time is the time lost in the starting of the green time interval when a traffic signal phase changes from red to green and previously stopped vehicles in the curb line queue need time to accelerate to the desired speed. Actual traffic data analytics from newly installed loop coil detectors at all approaching upstream road segments of major intersections on Sathorn Road in Bangkok, Thailand, are used to confirm that the vehicle flow is obstructed considerably by the large start-up lost time. In this paper, the effect of a large start-up lost time is evaluated in terms of the travel time of passenger cars in a calibrated microscopic traffic simulation. The evaluation is based on the simulation of the urban mobility platform, while the traffic signal lights at major intersections are based on the standard Synchro optimization software. By the simulation, the average travel time per vehicle increases from 4% to 37% when the start-up lost time is varied from a baseline value of 1 s to the maximum value of 15 s, which potentially occurred in the actual traffic data collection in this paper. In addition, the optimal traffic signal green phase lengths increase from 2% to 42%, depending on the volume-to-capacity ratio. The similar increasing trend of optimal green time and average travel time per vehicle is observed using theoretical analysis based on M/M/1 and D/D/1 queues to support the results from Synchro. Findings of this paper are beneficial for understanding the impact of start-up lost time at signalized intersections.