This report offers highway engineers guidance in designing interchanges so as to reduce the likelihood of truck accidents on highway interchanges. This report summarizes research showing that the interaction between truck dynamics and interchange geometry can contribute to rollovers, jackknifes, and other loss-of-control accidents. The research was conducted by the University of Michigan Transportation Research Institute (UMTRI) and supported by the Federal Highway Administration (FHWA). Engineers can apply corrective actions to six specific ramp design features that were found to contribute to truck accidents: poor transitions to superelevation, abrupt changes in compound curves, short deceleration lanes preceding tight-radius exits, curbs placed on the outside of ramp curves, lowered friction levels on high speed ramps, and substantial downgrades leading to tight ramp curves. Countermeasures for these design problems include incorporating a greater safety margin into formulations for side friction factors, reviewing and modifying posted speed limits, improving curve condition and downgrade signs at interchanges, increasing deceleration lane length, overlaying curbs with wedges of pavement or eliminating curbs altogether, resurfacing ramps with high-friction overlays, and redesigning sites where accidents are common. (Author/publisher)
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