Using Distributed Autonomous Adaptive Cruise Control Vehicles to Mitigate Congestion in a Two-Lane Traffic Flow

Steady advances in autonomous vehicle development are expected to lead to improved traffic flow in terms of string stability compared with that for human-driven vehicles. Fluctuation in intervehicle distances among a group of vehicles without string stability is amplified as it propagates upstream (rearward), which may cause traffic congestion. Since it will take a few decades for autonomous vehicles to replace all human-driven vehicles, it is important to tackle the problem of traffic congestion in a mixed flow of human-driven and autonomous vehicles. Communication technologies such as fifth-generation mobile communication systems, which are improving rapidly, enable vehicle-to-vehicle communication with a sufficiently small delay. We previously reported a strategy based on vehicle-to-vehicle communication for avoiding traffic congestion by using leader–follower control, which is a distributed autonomous control strategy. However, it was designed and evaluated for single-lane traffic. With substantial multilane traffic, congestion triggered by changes in vehicle velocity could appear more frequently and severely compared with that of single-lane traffic due to vehicles cutting in from other lanes. Use of our previously proposed strategy in this scenario could result in undesirable repetitive deceleration of the distributed autonomous adaptive cruise control (ACC) vehicles due to reduced spacing between a distributed autonomous ACC vehicle and the preceding human-driven vehicle. Here, we report a distributed autonomous ACC vehicle control strategy that prevents undesirable repetitive deceleration while satisfying the string stability condition. With the proposed control strategy, the reference acceleration is calculated as the weighted average of two control functions. One function is used to achieve string stability between two autonomous ACC vehicles, and the other is used to maintain a safe distance between an autonomous ACC vehicle and the preceding standard vehicle. We derive the condition for string stability of distributed autonomously controlled ACC vehicles and demonstrate the validity of the proposed control strategy using simulation.