ARSRPE Conference Paper Database

Heavy Vehicles and Speeding: Evidence from Traffic Survey Data

Friswell, Rena

Heavy Vehicles


The aim of this project was to look at the distribution patterns and patterns of speeding of heavy vehicles on the road as measured by traffic surveys conducted at 20 fixed speed cameras sites in NSW over the period 1999-2001. At each survey site, Trafficorder data captured the number of vehicles passing at particular times across the 24 hour period. Vehicles were classified by AUSTROADS class with light vehicles in classes 1 and 2 and heavy vehicles in classes 3 to 12. The results showed that heavy vehicles have a very different distribution to light vehicles on the road. Despite their overall much lower numbers on the road, heavy vehicles are, proportionately, most common in country areas and during the midnight to dawn period, but this is due to the concentration of light vehicles in metropolitan areas and during the daytime period. The results demonstrate that heavy vehicles were less likely to be speeding overall, but especially on metropolitan, unclassified and low speed zone roads. There was less difference in the speeding patterns of light and heavy vehicles on country non-urban roads, state highways and high-speed zones, especially 110km/h. In 110km/h limit regions heavy vehicles tended to speed at least as much as light vehicles and appeared to be responding to the upper speed limit for light vehicles rather than the lower speed requirement for heavy vehicles. Consistent with the finding of lower levels of speeding for heavy vehicles, the analysis showed that speed-related crash rates were lower for heavy vehicles, particularly on country non-urban roads, for state highways and 100km/h speed zones. Although country urban regions and speed zones of 80 and 90km/h had higher rates for heavy vehicles compared to light vehicles, the percentage of heavy vehicles that were speeding was still lower than for light vehicles.