Investigating safety impact of sun glare in urban tunnels based on cellular automata approach

This study applies a simulation-based traffic conflict technique to evaluate the hypothesis that sun glare under upper vents exerts negative impacts on traffic safety in urban tunnels. A modified cellular automata (CA) model is applied to simulate the deceleration behavior due to sun glare (DBSG) in real traffic. And the model is calibrated and validated against the empirical data. Conflict occurrences are generated through simulating vehicular interactions based on this model. Simulation experiments are conducted with different density and illuminance to evaluate the safety impacts of sun glare. Comparison of simulated conflict occurrences shows that rear-end conflicts occur more frequently as illuminance and density get higher. And the impacts of sun glare are more obvious on weak conflicts in moderate-density flow and more severe conflicts in high-density flows, respectively. To alleviate the negative impacts of sun glare, a sunshade system is designed based on the quantitative results.