Performance Comparison of Adaptive Cruise Control in Mixed Traffic Flow Considering Different Time Headway Policies

Emerging connected and autonomous vehicles (CAVs) technologies are expected to be the most promising technology for improving traffic efficiency and safety. However, high-level CAVs are unavailable in near future. As a low-level application of CAVs, adaptive cruise control (ACC) is widely applicable in the academy and industry. In the long term, ACC vehicles will co-exist with human-driven vehicles on the road. There is an urgent need to have a comprehensive understanding of driving behaviors for ACC in mixed traffic flow. For the ACC algorithms, the key component is the desired time headway policy, and it will directly affect vehicle safety and traffic efficiency. Currently, two types of desired time headway policies can be distinguished for ACC: constant time headway (CTH) and variable time headway (VTH). In this paper, the performance comparison of ACC in mixed traffic flow with different desired time headway policies is conducted. First, the string stability conditions of the mixed traffic flow with different desired time headway policies for ACC are analytically derived. Then, simulation experiments of mixed traffic flow with different penetration rates of ACC vehicles are conducted considering an on-ramp bottleneck. The safety and efficiency performance of the mixed traffic flow with different desired time headway policies of ACC vehicles are calculated. Results show that the VTH policy has better performance for improving safety and efficiency compared with the CTH policy.