Safety Implications of Converting Continuous Green T-Intersections Back to Conventional T-Intersections

Abstract

A continuous green T-intersection (CGT) is an innovative intersection that can improve the through traffic capacity by allowing major-leg vehicles on the top side of the T-intersection to pass through without stopping. Recently, traffic engineers decided to cease CGT operations at several T-intersections in Florida because of traffic safety concerns, conversion to a four-legged intersection, pedestrians’ demands, and non-compliance with the latest Manual on Uniform Traffic Control Devices. In this study, safety effects of recent conversions of CGTs back to conventional T-intersections in Florida are explored. An empirical Bayes (EB) before-and-after study method is adopted. The results indicate significant reductions in total, fatal-and-injurious, rear-end, and CGT-related crashes by approximately 30%–50% following the conversion. To validate the results, a cross-sectional analysis was conducted with new data from four states. The results are consistent for total, fatal-and-injurious, and CGT-related crashes with those from the before-and-after study. The results also show that crashes at CGTs can be minimized by providing a physical separation between the acceleration lane for the merging vehicles and the CGT through lane, along with other factors. Because Florida’s T-intersections that were converted back to the conventional design from CGT had no physical separation, the results showed a significant safety improvement following the conversion. Therefore, the decision to cease CGT operations at the Florida study sites was supported from the safety aspect. We concluded that safety at CGTs can be a concern compared to that at non-CGTs; however, it can be significantly improved by providing appropriate countermeasures.