TRUCK DESIGN, THE SHORTFALLS

The road safety matrix has been a useful tool to investigate road traffic crashes in- depth and to identify avenues to improve road safety. There are elements of heavy truck design that continue to precipitate or aggravate crashes. The factors are not novel yet appear to defy modern design. Factors of this type include design for minimum maintenance especially of brakes and tyres and other components of the drive train; strength of couplings of articulated vehicles; selection of coupling, trailer suspension and type-of-load combinations; loading practice, retention of load and elimination of the shifting of the load; vehicle components which fail under shock loading at the onset of a crash; compatible braking effect of trailer and tractor of articulated vehicles, and relatively low braking performance of heavy vehicles compared with other traffic units on level ground and on long steep descents. Truck occupant protection would be improved if occupants wore seat belts, and if design controls on cabin resistance to intrusion for forward impact and roll over and shifting of the load were introduced. Car occupant protection in collisions with trucks will be improved with the introduction of compulsory rear under- ride guards. In frontal collisions, overseas studies suggest that worthwhile improvements can be gained by the use of energy absorbing front under- ride guards. Further research is expected to confirm the practical and economic advantages. Energy absorbing front under- ride guards should replace bull bars but should provide a high level of truck occupant protection as do existing bull-bars. (TRRL)