HEAVY VEHICLE STABILITY AND ITS RELATION TO SAFETY

Road performance of heavy duty vehicles (HDV) depends on several parameters which can be grouped as human factors, weights and dimensions, and vehicle stability. It might be said that in the end all accidents involving HDVs are human factors related. However, assuming the same driving operations, a comparative analysis of HDV stability can be carried out, under normal and critical conditions. It is now known that establishing standards for weights and dimensions does not guarantee that a vehicle performs safely on the road, because different load distributions might change the stability of trucks and trailers. Thus, using a computer program developed at the University of Michigan Transportation Research Institute, a parametric study of two types of heavy vehicles stability and its relation with potential accident conditions is presented. The vehicle configurations are of common use in the US, Mexico and Canada. The stability analysis presented includes simulation of overloaded conditions and its influence on breaking under constant deceleration, high and low speed off-tracking, rollover threshold determination and maneuverability. Results from these simulations show the importance of overloading as a potential cause for highway accidents involving HDVs.