Automated Traffic State Optimization in the Weaving Area of Urban Expressways by a Reinforcement Learning-Based Cooperative Method of Channelization and Ramp Metering

Abstract

The traffic congestion problem on urban expressways, especially in the weaving areas, has become severe. Some cooperative methods have been proven to be more effective than a separate approach in optimizing the traffic state in weaving areas on urban expressways. However, a cooperative method that combines channelization with ramp metering has not been presented and its effectiveness has not been examined yet. Thus, to fill this research gap, this study proposes a reinforcement learning-based cooperative method of channelization and ramp metering to achieve automated traffic state optimization in the weaving area. This study uses an unmanned aerial vehicle to collect the real traffic flow data, and four control strategies (i.e., two kinds of channelization methods, a ramp metering method, and a cooperative method of channelization and ramp metering) and a baseline (without controls) are designed in the simulation platform (Simulation of Urban Mobility). The speed distributions of different control strategies on each lane were obtained and analyzed in this study. The results show that the cooperative method of channelization and ramp metering is superior to other methods, with significantly higher increases in vehicle speeds. This cooperative method can increase the average vehicle speeds in lane-1, lane-2, and lane-3 by 14.51%, 14.81%, and 37.03%, respectively. Findings in this study can contribute to the improvement of traffic efficiency and safety in the weaving area of urban expressways.