Abstract
Traffic oscillations often occur in road traffic, they make traffic flow unstable, unsafe and inefficient. Emerging connected and autonomous vehicle (CAV) technologies are potential solutions to mitigating the traffic oscillations for the advantages that CAVs are controllable and cooperative. In order to study a control strategy and the effectiveness of CAVs in mitigating traffic oscillations and improving traffic flow and analyse the characteristics of homogeneous traffic flow made up of CAVs and heterogeneous traffic flow made up of CAVs and RVs when traffic oscillations appear in traffic flow. Firstly, the formation and propagation of traffic oscillations in a platoon of RVs are simulated and analysed. Then, a car-following control model is built to control the longitudinal motion of CAVs, and real-time information of preceding CAV is used in the model and this can make the motion of CAVs more cooperative. The model reflects an idea named “slow-in” and “fast-out,” and this idea is helpful to mitigate traffic oscillations. Then, numerical simulations of homogeneous traffic flow of a platoon of CAVs and simulations of heterogeneous traffic flow containing CAVs and RVs are conducted, and different penetration rates (0, 0.2, 0.4, 0.6, 0.8, and 1) of CAVs are considered in the simulations of heterogeneous traffic flow. The characteristics and evolution of traffic flow are analysed and some indexes reflecting traffic efficiency and stability are calculated and analysed. Simulation results show that there are smaller velocity fluctuation, less stopping time and shorter length of road occupied when vehicle platoon contains CAVs (penetration rates are from 0.2 to 1) compared to the platoon containing only RVs (without CAVs). As for the heterogeneous traffic flow containing CAVs and RVs, these three indexes decrease with the increase of penetration rates (from 0.2 to 1) of CAVs. These results indicate that CAVs with the car-following control model in vehicle platoon are beneficial for mitigating traffic oscillations and improving traffic flow.
Highlights
Tra c oscillations o en happen in road tra c
Tra c oscillations have extremely negative e ects on tra c ow, e.g., high risk of accidents, high fuel consumptions, and emissions and low tra c e ciency
Ge et al [25] designed a longitudinal controller for a connected and autonomous vehicle (CAV), it can receive real-time motion information from one or more preceding connected vehicle (CV) driven by human, and field experiments were conducted and the results shown that the control strategy of CAV was helpful to mitigate traffic waves and improve safety and energy efficiency
Summary
Tra c oscillations o en happen in road tra c. Ge et al [25] designed a longitudinal controller for a CAV, it can receive real-time motion information from one or more preceding CVs driven by human, and field experiments were conducted and the results shown that the control strategy of CAV was helpful to mitigate traffic waves and improve safety and energy efficiency. Considering the effectiveness of the idea of “slow-in” and “fastout” [7] in mitigating traffic oscillations and considering the technologies that CAVs can share real-time state information with each other, we propose a car-following control model for CAVs to make CAVs move cooperatively and to mitigate traffic oscillations based on this idea as well as this technologies in this paper.
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