Impacts of Signal-Related Characteristics on Crash Frequency at Urban Signalized Intersections

Abstract

The effect of signals at urban intersections is critical in reducing death, injuries, and property loss. Unfortunately, the signal-related factors that can effectively reduce crash frequencies have not been adequately explored. This study investigates the impacts of signal-related, traffic, and highway geometric characteristics on crash frequency at urban signalized intersections. Seven-year crash data from 381 intersections in Illinois, United States of America, was used to estimate a random-parameters negative binomial model. The estimation results showed that a unit increase in the number of signal phases would increase crash frequency by 0.4. Additionally, the ratio of traffic volume on the major road to the traffic volume on the minor road was shown to unambiguously increase crash frequency. On the other hand, the number of approach lanes and the maximum green time of different approaches in a signal revealed an ambiguous effect, whereas increasing crash frequency on 76.33%, and 93.32% and decreasing it on the remaining 23.67%, and 6.68% of the signalized intersections, respectively. Although, this study is exploratory in nature, the results showed that ignoring these factors at urban signalized intersections would lead to the design of ineffective safety-related countermeasures, and the impacts could be underestimated by 5% to 25%.