Analysis of linear internal stability for mixed traffic flow of connected and automated vehicles considering multiple influencing factors

The stability of traffic flow reflects the ability to resist traffic perturbation and reveals the formation mechanism of congestion in a non-bottleneck link. To study the stability of mixed traffic flow in the non-fully connected and automated vehicles (CAVs) environment, this paper takes time delay, platooning intensity and CAVs degradations into consideration. Firstly, the vehicle types in the mixed traffic flow are analyzed considering degraded CAVs. Then time delays of different types of vehicles are discussed. The proportion of each type of vehicle under the influence of platooning intensity is determined. Based on this, the linear internal stability condition of mixed traffic flow is derived by using the characteristic equation-based method. The stability condition is related to CAVs degradations, time delay, and platooning intensity. In addition, the influence of CAV penetration rates, platooning intensity, and time delay on traffic stability are analyzed. Finally, the simulation experiments are carried out to verify theoretical results. The results show that: (1) CAV penetration rates and platooning intensity are conducive to maintaining the stability of the mixed traffic flow; (2) CAVs degradations and time delay have a negative effect on stability; (3) when the penetration rate of CAVs is more significant than 90.4%, the traffic flow is stable in the entire speed range. To a certain extent, these conclusions can enrich and expand the existing research results on the stability of the mixed traffic flow.