Alternate Ramp Merging Strategy for Connected Vehicles Based on Roadside Unit Support

Background: Uncooperative driving behavior in merging areas significantly increases traffic congestion and conflicts, resulting in reduced safety and comfort of vehicle travel. With the advancement of technologies for intelligent connected environments, vehicle-to-infrastructure (V2I) technologies have been implemented to enable real-time data exchange between vehicles and infrastructure. This exchange allows vehicles to make driving strategies and motion plans based on roadside information. Therefore, it becomes particularly important to develop effective merging strategies. Various methods, both patented and non-patented, have been proposed to solve the merging challenges, aiming to optimize data exchange and enhance the formulation of driving strategies. Objective: In this paper, a strategy is proposed using roadside information to guide vehicles alternately merging, aiming at solving the safety and traffic efficiency problems in the ramp merging area, which has two main objectives: guiding vehicles to merge smoothly and safely under high traffic flow to reduce vehicle conflicts and calculating their recommended velocity through connected information to minimize congestion. Methods: A roadside system was designed to guide vehicles to merge alternately. GPS information from connected vehicles is utilized to achieve cooperative perception and localization. A time-tomerge (TTM) algorithm was developed to optimize vehicle trajectories combined with the responsibility- sensitive-safety (RSS) theory, which assigns merge sequence and recommended velocity to each vehicle based on the actual traffic conditions. Results: Simulation results indicate that this merging strategy eliminates conflicts and suppresses the formation of deceleration waves compared to the first-in-first-out (FIFO) strategy. Compared to the natural merging of independently controlled vehicles, it results in a 33.71% increase in average vehicle velocity and a 14.68% reduction in average travel time through the merge area. Conclusion: This strategy improves driving safety and efficiency by enabling vehicles to reach a common understanding of the merging sequence, and the more congested the traffic, the more significant improvement in merging efficiency.