Developing a Framework for Evaluating and Selecting Curve Safety Treatments

Horizontal curve operations and safety are affected by various geometric characteristics, such as radius, superelevation rate, deflection angle, and cross-sectional width; and pavement characteristics like skid number. Identification and application of cost-effective safety treatments requires application of a consistent analysis framework that accounts for these variables. In this paper, a framework is presented that allows practitioners to assess the safety performance of a curve of interest using margin of safety, which is defined as the difference between side friction demand and side friction supply; and crash frequency estimates obtained from safety prediction models that account for the influence of curve geometry and pavement friction. The analysis framework is formulated as a spreadsheet program that automates the numerous required calculations, and provides the analyst with insights into whether a curve should be considered for pavement-based treatments like a high-friction surface treatment or an increase in superelevation rate.