Determining Skid Resistance Needs on Horizontal Curves for Different Levels of Precipitation

Abstract

Horizontal curves are a major cause of crashes that lead to fatal and serious injuries. Much research has been conducted on the safety implications of geometric and traffic characteristics of curves. Variables describing curve geometry and speed have been incorporated into safety prediction methodologies. However, relatively less research has been conducted on the effects of pavement friction and weather data on safety. The objective of this study is to develop a methodology for determining the pavement friction needs for different levels of precipitation. To accomplish the study objective, rural two-lane, four-lane undivided, and four-lane divided horizontal curve data from Texas were used. Safety prediction models were developed that included traffic and geometric characteristics, skid number, and annual precipitation rate. These models were then used to develop the guidelines for assessing the safety performance of a curve of interest by accounting for curve geometry, pavement skid resistance, and exposure to the wet-weather conditions that are most relevant for considerations of skid resistance. For conducting a planning-level analysis to identify candidate sites for pavement friction treatments, researchers developed thresholds based on the combined effect of skid number and annual precipitation variables. Researchers also provided skid number thresholds for high-priority sites for two example locations that experience significantly different levels of annual precipitation.