Study Details

Study Title: Two-Way Left Turn Lane or Raised Median? A Truck Safety Based Study

Authors: Qu et al.

Publication Date:SEP, 2020

Abstract: Introduction: Due to their size and weight, trucks require more space and time to make left turns when exiting or entering a roadway. Therefore, appropriate median treatments are critical for roadways with substantial truck traffic. The two-way left-turn lane (TWLTL) and raised median (RM) are the two types of median most commonly used to improve roadway mobility and manage roadway accessibility. However, previous studies on these median treatments have focused primarily on the general traffic con­ditions and geometric roadway features without considering the truck traffic impact. Method: To fill this gap, this study investigates the truck impacts on TWLTL and RM by considering two major influencing factors - truck percentage and roadway access point density. First, a negative binomial regression is developed to analyze the relationship between crash frequency and various influencing factors. Next, the crash rate difference analysis between the TWLTL and RM is conducted to identify critical points for these two factors. Results: The findings indicate that, compared with RM, TWLTL has significantly higher crash frequency, especially for roadways with a higher percentage of trucks. This suggests that the percentage of trucks should be taken into consideration when selecting an appropriate type of road­way median.

Study Citation: Qu, W., T. Tao, Q. Zhao, Q. Sun, and Y. Qi. "Two-Way Left Turn Lane or Raised Median? A Truck Safety Based Study". Journal of Safety Research, Vol. 74, (2020) pp. 109-117.

Related Citations: Qu, W., T. Tao, Q. Zhao, Q. Sun, and Y. Qi. "Two-Way Left Turn Lane or Raised Median? A Truck Safety Based Study". Presented at the 98th Annual Meeting of the Transportation Research Board, Paper No. 19-04386, Extended abstract only, Washington, D.C., (2019).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Access management

Countermeasure: Replace TWLTL with raised median

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.71928.142 StarsAllAllPrincipal Arterial OtherUrban