Safety Assessment of Cooperative Vehicle Infrastructure System-based Urban Traffic Control

Cooperative vehicle infrastructure system (CVIS) or connected vehicles, formerly known as IntelliDrive, has emerged and is expected to provide unprecedented improvements in mobility and safety. A recent study developed a CVIS-based urban traffic control system that does not require a stop-and-go style traffic signal. A simulation-based study on the CVIS-based control found significant improvements in mobility, energy (i.e., reductions in fuel consumption), and greenhouse gas emissions. However, safety was not considered in that study. This paper investigated safety aspects of the CVIS-based urban traffic control system by applying surrogate safety assessment model (SSAM). The purpose of this study was to assess whether safety has been impacted and, if so, how much safety has been compromised due to reduced time headways between vehicles and higher acceleration/deceleration rates under the CVIS-based urban traffic control system. A simulation-based case study was performed on a hypothetical arterial consisted of four intersections with four traffic congestion cases covering high to low volume conditions. As a 2 result, the CVIS control, when compared to the coordinated actuated control, reduced the averages of time to collision (TTC) and post encroachment time (PET) by 0.69 and 1.94 seconds, respectively. Note that shorter TTC and PET indicate more dangerous situation. However, it was discovered that the number of rear-end conflict events decreased by 58% under the CVIS-based control, indicating more safer driving conditions would be achieved with the CVIS-based control system.