Development of Crash Prediction Models for Curved Segments of Rural Two-Lane Highways

Crash prediction models for curved segments of rural two-lane two-way highways were developed. The modeling effort included the calibration of the predictive model found in the Highway Safety Manual (HSM) as well as the development of Utah-specific models developed using negative binomial regression. The data for these models came from randomly sampled curved segments in Utah, with crash data coming from years 2008-2012. The calibration factor for the HSM predictive model was determined to be 1.50 for the three-year period and 1.60 for the five-year period. A negative binomial model was used to develop Utah-specific crash prediction models based on both the three-year and five-year sample periods. The significant variables were average annual daily traffic, segment length, total truck percentage, and curve radius. The main benefit of the Utah-specific crash prediction models is that they provide a reasonable level of accuracy for crash prediction yet only require four variables.