Citation

Ervin RD. HSRI Res. Rev. 1980; 10(5).

Copyright

(Copyright © 1980, University of Michigan Highway Safety Research Institute)

DOI

unavailable

PMID

unavailable

Abstract

Four types of unintended responses of heavy trucks to braking or steering inputs are discussed: loss of directional control during braking (single unit truck front-wheel lockup and rear spin out, and tractor-semitrailer jackknife and trailer swing); directional instability during cornering; roll instability (rollover); and full trailer amplified directional motions. Design features of heavy trucks are examined which differ from those of cars and contribute to the unintended responses: fore-aft load distribution and the proportioning of brakes and spring stiffnesses, height of the payload, and the presence of articulation joints. The relationship between truck dynamics and accidents is discussed. Among the various accident types characteristic of heavy trucks and truck combinations, the jackknifing of empty tractor-semitrailers and the rollover of loaded units appear to be the most prevalent unintended responses. The accident-avoidance lane change maneuver is considered most likely to cause premature rollover of the trailer.