Mixed traffic group throttling control strategy for traffic bottleneck of expressway

Considering the lane reduction bottleneck of expressways under mixed traffic condition composed of human-driven vehicles (HVs) and connected and automated vehicles (CAVs), a novel speed harmonization control strategy (throttling control strategy for short) was developed from the viewpoint of group control. A speed controller for the leading CAV was designed on the basis of the bottleneck traffic state and the Greenshields model. A nonlinear controller for the target changing was developed for the control during the CAV throttling group formation. A platoon-like controller for the CAV throttling group was built, and the group formation and group speed were thereby regulated dynamically according to the bottleneck traffic state. The speed control method for the leading CAV was combined to regulate the vehicles overtaking each throttling group periodically. A longitudinal safety controller for the CAV was presented to resolve the vehicle safety problem in the processes of group formation and group evolution. Simulation results show that, on the bottleneck road of the expressway, compared with the traditional traffic system, the proposed dynamic throttling control strategy is applied when the CAV penetration rate reaches 5% and vehicle flow is 2 000, 3 000, 5 000 and 6 000 vch · h-1, respectively, the corresponding traffic efficiency improves about 5. 87%, 16. 97%, 11. 07%, and 10. 25%, respectively. On an expressway bottleneck road with a fixed traffic flow of 3 000 or 6 000 vch · h-1, compared with the traditional traffic system, the traffic efficiency of the controlled traffic system can be enhanced by around 24% when the CAV penetration rate reaches 10%, 20%, and 30%, respectively. According to the analysis of space headways, the controlled CAVs can avoid collision during the entire throttling process and keep a safe distance of more than 9 m from their predecessors. Therefore, the throttling control strategy is effective in dealing with the bottleneck problem of expressway. 3 tabs, 15 figs, 30 refs. © 2022 Chang'an University. All rights reserved.