Effects of Cross-Slope Break on Roadway Departure Recovery for Trucks on Horizontal Curves

A 2009 crash involving a tanker truck that departed the roadway on a freeway connection ramp led the National Transportation Safety Board to suggest a review of current AASHTO policy for pavement–shoulder cross-slope breaks on horizontal curves to determine whether updates to the design criteria were needed. As part of NCHRP Project 03-105, the research team reviewed and summarized existing policies and conducted a pair of studies focusing on large trucks on horizontal curves. Researchers conducted a vehicle dynamics simulation study and a crash-based study; both were designed to identify patterns and trends in roadway departure crashes involving large trucks and to develop recommendations for corresponding revisions to AASHTO policy for designing cross-slope breaks on horizontal curves. In the vehicle dynamics simulation study, researchers developed and analyzed results from roadway departure models for a tractor single-van trailer truck, a tractor tanker trailer truck, and a tractor double-van trailer truck for various combinations of roadway departure path, approach speed, superelevation, and cross-slope break. This paper summarizes existing policy, describes the study method, and presents findings from the vehicle dynamics simulation study. Results indicate that no changes need to be recommended for AASHTO’s policy on cross-slope break.