The dynamic performance of large combination vehicles (road trains) has a significant effect on road safety. The Australian Road Research Board (ARRB) was commissioned by the Main Roads Department Western Australia (MRD WA) to investigate four aspects of road train operations; their dynamic behaviour under offtracking, stability, trailing fidelity, perception by other motorists under other vehicle overtaking behaviour, and a roadside questionnaire of driver attitudes to the presence of road trains. Three road train configurations were tested in August 1988, a double bottom, triple bottom and a rigid truck with three trailers, all side tipping ore carrying vehicles operated by Gulf Transport Co. Pty Ltd. A triple bottom cattle train operated by Petherick Road Transport was partially tested. This paper describes the research procedure, results, the development of regression equations to enable vehicle comparisons of rearward amplification and computer simulation for the dynamic stability aspect of the vehicles operated by Gulf Transport. The data acquired from this field exercise revealed that the dynamic stability (rearward amplification) of road train configurations is dependent on vehicle configuration (number of trailers), vehicle speed and driver steer input rate. Analysis of the data established that for the Gulf vehicle combinations, the triple had an increase in rearward amplification ratio of 58 per cent over the double, and the rigid plus three an increase of 16 per cent over the triple at vehicle speeds of 80 km/h. At vehicle speeds of 95 km/h the increase in rearward amplification ratios were 82 per cent and 14 per cent respectively. Further research should be carried out on more `typical' types of road trains to complement this data and provide regulatory authorities with instant comparisons of the dynamic performance of various road train configurations (A).
Abstract