Technique for Identifying Problem Downgrades

A simple technique for identifying downgrades prone to runaway truck accidents has been developed and applied to several downgrades in West Virginia. Using geometric, environmental and accident data from 15 downgrades, an heuristic technique was formulated and tested. Plots of cumulative degree of curve versus cumulative distance from crest of grade appeared to be a useful tool in identifying problem downgrades. Concave upward curves were good predictors of high runaway truck accident rates. Irregular plots with frequency or sharp discontinuities could be used to identify runaway truck accident locations since trucks usually encounter problems at points of sharp horizontal curvature. Conversely, convex upward curves, or smooth curves with few discontinuities, generally had a smaller number of runaway truck accidents. There was good correlation between runaway truck accident rate and slope of the cumulative degree of curvature plot.