| Under connected vehicles and autonomous driving environment, vehicles are able to communicate and even collaborate with each other. This research developed an optimization-based model to optimally control highway and on-ramp vehicles simultaneously with the assumption that all vehicles are connected and controlled automatically. This control strategy was tested using VISSIM and the C2X module included in it. Some empirical ramp control strategies, including dynamic speed limit, gradual speed limit, and collaborative lane change, were first simulated under various traffic conditions to obtain some preliminary results. The results suggest that the two collaborative lane change strategies perform equivalently better in terms of average speed, average delay time, and throughput; while speed limit control strategies are less effective than lane-change strategies. The gradual speed limit control strategy and a benchmark case without considering any control strategies were further compared with the proposed optimization-based control model. The proposed optimization-based model is proved to perform well under different traffic conditions and its benefits become more significant as both the highway and ramp are not saturated. It is also concluded that the proposed optimization-based model can effectively coordinate all vehicles and improve safety. |
