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In order to analyze the impact of ramp convergence in merging area on the dynamic characteristics of expressway mainline traffic flow under the mixed traffic flow environment composed of connected and automated vehicle (CAV) and humandriven vehicle (HV), this paper selects the intelligent driver model (IDM), the adaptive cruise control (ACC) car-following model, and the cooperative adaptive cruise control (CACC) car-following model to model the HV, the DCAV (degraded connected and automated vehicle), and the CAV following behavior, respectively. The proportions of different types of vehicles are determined by platooning intensity, and the effects of changes in penetration rate on the dynamic characteristics of mainline traffic flow on expressways are investigated in terms of operational efficiency, traffic safety, emission, and fuel. The results show that the increase of penetration rate is more significant to the improvement of free flow operation efficiency compared with congested flow, and can effectively inhibit the diffusion of blockage to the upstream. With the increase of penetration rate, the overall safety of mainline mixed traffic flow is improved based on time-to-collision (TTC) analysis. However, when the proportion of connected and automated vehicles is 0.7, the mainline mixed traffic flow locally has the highest risk of rear-end collision, and the time exposed time-to-collision (TET) and time integrated time-to-collision (TIT) achieve peak values. In addition, increased penetration rate significantly reduces exhaust emissions and fuel consumption in mixed traffic flows.
Hu et al. (Wed,) studied this question.