A signal control model integrating arterial intersections and freeway off-ramps

Vehicles on urban freeway off-ramps often have difficulty in exiting due to congestion on the arterial routes. The resulting queue on the off-ramp generates a spillover onto the mainstream of the urban freeways, leading to serious problems such as decreased capacity and traffic safety. In this study, a signal control model for minimizing the total delay of off-ramps and connected downstream arterial roads is developed. The results demonstrate the proposed model's ability to reduce the delay of off-ramp and freeway mainstream. The developed model calculates an optimal signal time at off-ramps and arterial intersections by a linear programming technique with a variety of variables such as traffic volume, link length, and queue length. The simulation results show that as the traffic volumes of both off-ramps and arterials approach the saturation flow, the proposed model can increase the number of throughputs at off-ramps, decrease the average delay of whole links, and prevent the decrease of capacity on the mainstream of urban freeways by reducing the queue length at off-ramps. Especially, the reductions in the average delay time of whole links are 21.5% and 13.0% compared to T7F model and Sequential Control Model, respectively.