Impact of side traffic barrier features on the severity of run-off-road crashes involving horizontal curves on non-interstate roads

Objective: Reviewing the literature of run-off-road (ROR) crashes, there is limited knowledge in terms of crashes involving side (longitudinal) traffic barriers on curved segments. For instance, despite the valuable results found in past simulation and field crash tests, no study has been conducted using actual crash data analysis to evaluate the safety performance of side traffic barriers on horizontal curves of non-interstate roads. This paper aims to fill this gap. For this purpose, an actual crash data analysis was conducted to identify factors impacting the severity of crashes involving side traffic barriers on horizontal curves of non-interstate roads in Wyoming. Method: A field inventory was conducted to collect type, height, side-slope rate, lateral offset, and post-spacing of over 105 miles of side traffic barriers located on horizontal curves of non-interstate roads in the state of Wyoming. The data collected includes 25% of all traffic barriers (located on tangent and curved segments) on non-interstate roads in Wyoming. Then, the data was combined with historical crashes, road geometric features, and traffic volume data. For the statistical analysis, random-parameters ordered logit was utilized to model the effect of parameters affecting the crash severity. Results: Post-spacing and height of side barriers were identified to be statistically significant on the crash severity on horizontal curves of non-interstate roads. Side box beam barriers with a post-spacing of 6.1 ft were least likely to result in a fatal or severe injury crash. On the other hand, side box beam barriers with a height shorter than 25 inches showed a high probability of fatalities or severe injuries. It was found that ROR crashes tended to be less severe on side W-beam barriers having a height between 24 and 31 inches. Conclusions: Side traffic barriers with a short height are not recommended to be used on horizontal curves. Based on the results found in this research and past similar studies, it is recommended to consider a height taller than recommendations given by the roadside design guide (AASHTO RDG 2011) on curved segments. Post-spacing of 6.1 ft was found to be recommended to be considered for side box beam barriers