Dynamic Traffic Flow Equilibrium and Coordinated Signal Control for Ramps and Adjacent Intersections

Ramp congestion significantly hampered travel efficiency into urban expressways; about 30% of the total travel time is taken waiting at the expressway entrance during rush hours. This study is specifically concerned with ramps and an adjacent intersection, area traffic flow characteristics are analyzed, and the dynamic traffic flow equilibrium model is discussed with the objective to maximize travel capacity. Compared to a standalone approach, coordinated on-ramp and adjacent intersection control is presented, which has the advantage that cycle and phase information of upstream traffic signal can be used in the algorithms for ramp metering optimization. In analysis of the basic difficulties and limitations of theoretical models as well as continuous or interrupted traffic flow model during the practical application, innovative algorithm solving steps based on corridor traffic state is also discussed. With the model calculation results, a collaborative optimization control method to enhance capacity and alleviate congestion is applied to ramp metering and signal timing. Mostly, as a demonstration project of Shanghai expo ITS integrated system, a traffic flow model and coordinated control strategy are applied to the case of West Yan'an road with one adjacent on-ramp. A simulation study was conducted to compare on-ramp control performance between coordinated and a standalone approaches. The optimization control parameters are computed, and the simulation evaluation results show that with the coordinated control, traffic capacity increases by 18.63%, and the vehicle delay decreases by 21.3%.