Impact of connected and autonomous vehicles on traffic efficiency and safety of an on-ramp

In this paper, the impacts of connected and autonomous vehicles (CAVs) on traffic efficiency and safety are numerically investigated. An on-ramp cellular automata (CA) model considering safe distance and interconnectivity is proposed and traffic flows under different CAV penetrations and distributions of CAVs are simulated. The outflow increases as the CAV penetration rate increases when the inflows are large, while the growth rate is insignificant when the inflows are small. The average speed distribution results also illustrate the positive impact of CAVs on traffic efficiency. In terms of traffic safety, the time-to-collision (TTC) results indicate that CAVs promote traffic safety in congested conditions. The criticality index function (CIF) results indicate that the mixed flow is still safe. We also proposed an evaluation index under emergency braking. Although CAVs have certain safety disturbance effects, they ensure that all vehicles are safe and alleviate stopand-go traffic.