Abstract:
This study aims to quantify the safety impacts of Connected and Automated Vehicles (CAVs) in mixed traffic environments in three calibrated and validated urban road networks including Manchester (UK), Leicester (UK), and Athens (GR). Road safety impacts were investigated through traffic microsimulation techniques combined with application of the Surrogate Safety Assessment Model (SSAM). Behaviours of CAVs were modelled based on a comprehensive literature review and discussions with experts. The estimated number of conflicts, extracted from the microsimulation and SSAM approach, were converted to the number of crashes by using a probabilistic method. Results revealed a significant improvement in case of passenger car fleet scenarios in all three test networks. However, the mixed fleet scenarios involving freight and public transport vehicles showed added complexities due to non-homogeneity in vehicle characteristics. In this context, limitations of microsimulation and SSAM have also been identified while recommendations have been made for methodological improvements. Overall, the findings of this research provide several useful insights by using a practical procedure to estimate safety impacts under mixed traffic environment. Future research and field trials should focus on addressing the challenges of maintaining safety in the early and transition phases of the deployment of CAVs.
