This study and others have shown that trucks already exceed the legal speed limits. Truck drivers are travelling at speeds they consider safe in respect of their vehicle, the traffic volume, road environment and police activity. The principal aim of this study was to examine the effect of the increase in the heavy vehicle speed limit on rural roads from 80 to 90 km/h on 1 January 1987 in every state except Queensland, and in the ACT. Mean free speeds were used to gauge whether there had been any significant effect of the speed limit increase on driver behaviour and road safety. The sampling methods used in this study are biased towards over sampling of trucks and elevating truck mean speeds. Scant attention has been given to sample design in most of the previous studies cited. Articulated vehicle mean free speeds have increased in four States, as has the percentage travelling faster than 90 km/h. This included Queensland, the control State for the study. Car speeds remained stable during the study period. There has been an increase in the number of platoons led by cars over the study period. There was a decline in the number of articulated led platoons. Speed differentials have been reduced from 10 km/h to 8 km/h for the articulated/car vehicle mixes. Thus a successful decrease in 'speed dispersion' has been accomplished. Analysis of crashes in Victoria and Western Australia showed no significant changes which could be attributed to the change in heavy vehicle speed limit. (A)
Abstract