Effect of Arterial Signal Coordination on Safety

Traffic signals are coordinated to improve traffic mobility, but the impact of coordination, particularly specific coordination solutions, on safety is not well known. Engineers who set coordinated signals can use several tools to improve traffic mobility but have no tool with which to account for safety. A study was done on the impact of arterial signal coordination on the frequency and severity of rear-end and right-angle collisions the two types of crashes that are both prevalent at signalized intersections and likely affected by signal coordination. Multinomial logit models were developed to estimate crash likelihood in short time intervals on arterial intersection approaches, as well as the severity of crash outcome. The obtained models were used to investigate the safety impact of signal coordination and other road and traffic variables. The following results were determined: (a) signal coordination can significantly affect crash likelihood and severity; the concentration of vehicle arrivals in the second half of a green phase is associated with significantly lower crash likelihood and severity; (b) certain components of the traffic flow are most susceptible to crashes; (c) short distances between intersections and short cycle lengths are associated with a lower risk of crash; and (d) the presence of a right-turn bay is associated with a considerable improvement in safety manifested by a lower risk of rear-end and right-angle collisions. The developed models can be used as a tool for evaluating alternative signal coordination plans for safety.