Study Details

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

Authors: Lee et al.

Publication Date:APR, 2020

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.

Study Citation: Lee, J., M. Abdel-Aty, and A. El-Urfali. "Safety Implications of Converting Continuous Green T-Intersections Back to Conventional T-Intersections". ASCE's Journal of Transportation Engineering, Part A: Systems, 146(4): 04020016 (2020).

Related Citations: Lee, J., M. Abdel-Aty, and A. El-Urfali. "The Safety Implications of the Conversion of Continuous Green T-Intersections Back to Conventional T-Intersections". Presented at the 98th Annual Meeting of the Transportation Research Board, Paper No. 19-00233, Extended abstract only, Washington, D.C., (2019).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Intersection traffic control

Countermeasure: Convert continuous green T-intersections to conventional T-intersections

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.66533.54 StarsAllAllAllUrban and suburban
0.50849.24 StarsAllK,A,B,CAllUrban and suburban
0.74725.34 StarsAllOAllUrban and suburban
0.52847.24 StarsRear endAllAllUrban and suburban
0.55454 StarsOtherAllAllUrban and suburban
0.9594.13 StarsSingle vehicleAllAllUrban and suburban
2.501-150.13 StarsOtherAllAllUrban and suburban
0.56943.14 StarsOtherAllAllUrban and suburban