Modeling the Safety Benefits of Converting Signalized Y Shaped Junctions to Signalized T Junctions

Junctions are basic joints of road network and their models affect traffic operation and safety greatly. There are quite number of Y shaped junctions at the highway. The existence of such abnormal junctions lowers operation efficiency and triggers traffic accidents. In the rebuilding constructions, T shaped junctions may be new builds but often are converted from Y shaped junctions. For more engineering applications, there is a need to estimate the safety effects of conversions. Several studies have estimated reductions in crashes and severity; however, these results pertain mainly to conversions from Y junctions without signal control. Results for conversions from signalized Y junctions have been less conclusive. Our study aimed to fill this void by estimating the safety performance of converting signalized Y shaped junctions to signalized T shaped junctions. Several cities in Jiangsu province along the national highway G205 helped to identify in the recent past. The empirical Bayes method was used to estimate the safety effects of conversations. The results indicated a safety benefit for converting signalized Y shaped junctions to T shaped junctions. There were reductions in both total and injury crashes, with a larger benefit for non-vehicle injury crashes. Further analysis indicated that the safety benefit of T shaped junctions for total crashes decreased as traffic volumes increase, a result that suggests the need for the development of a crash modification function (CMF), a task for which more data would be required.