Modeling Geometric Design Consistency and Road Safety for Two-Lane Rural Highways in the West Bank, Palestine

Abstract

This study investigates the effect of geometric design consistency on road safety in the West Bank. Studies have shown that operating speed, vehicle stability, alignment indices, and driver’s workload are the common consistency measures that might affect safety. A total of 118-km two-lane rural highways in the West Bank, Palestine, were studied based on limitations of available data. Comprehensive geometric and operating data for the selected highways obtained from field survey, maps, and official sources were used to investigate the effect of design consistency measures on road safety. Crashes for years 2008–2012, totaling 263, were used for model development using the generalized linear regression approach. Tested models were statistically significant at 95%, and adopted models showed acceptable levels of goodness of fit. The recommended model performed well across additional highway sections, additional years of data, validation of algorithm, and “%error” with a high linear correlation. The study adds to the evidence that several geometric design consistency measures contribute to roadway safety. The significant measures for the two-lane rural highways in the West Bank were segment length, traffic volume, difference between operating and design speeds, absolute difference in the 85th percentile speeds between successive design elements, and the ratio of individual curve radius to the average radius. The practical implication of this study, in addition to being able to predict crashes based on the recommended measures, highway designers should pay careful attention to inconsistent designs of two-lane rural highways to reduce their crash frequency.