Investigating the effect of geometric dimensions of median traffic barriers on crashes: Crash analysis of interstate roads in Wyoming using actual crash datasets

Abstract

Introduction: Despite the numerous safety studies done on traffic barriers' performance assessment, the effect of variables such as traffic barrier's height has not been identified considering a comprehensive actual crash data analysis. This study seeks to identify the impact of geometric variables (i.e., height, post-spacing, sideslope ratio, and lateral offset) on median traffic barriers' performance in crashes on interstate roads.

Method: Geometric dimensions of over 110 miles median traffic barriers on interstate Wyoming roads were inventoried in a field survey between 2016 and 2018. Then, the traffic barrier data collected was combined with historical crash records, traffic volume data, road geometric characteristics, and weather condition data to provide a comprehensive dataset for the analysis. Finally, an ordered logit model with random-parameters was developed for the severity of traffic barrier crashes. Based on the results, traffic barrier's height was found to impact crash severity.

Results: Crashes involving cable barriers with a height between 30″ and 42″ were less severe than other traffic barrier types, while concrete barriers with a height shorter than 32″ were more likely involved with severe injury crashes. As another important finding, the post-spacing of 6.1-6.3 ft. was identified as the least severe range in W-beam barriers.

Practical applications: The results show that using flare barriers should reduce the number of crashes compared to parallel barriers.

Keywords: Crash severity; Median traffic barrier; Random parameters ordered logit; Traffic barrier dimensions; Wyoming.