A new study from Adelaide University’s Centre for Automotive Safety Research (CASR) has found speed limits in Australia are not sufficiently matched to the risk to road users should a crash occur.
CASR Senior Research Fellow Dr Sam Doecke and Deputy Director Associate Professor Matthew Baldock analysed eight years of data from South Australia and New South Wales to calculate the fatal crash rate by speed limit.
This was then used to examine the degree to which speed limits have been set in accordance with the Safe System, the nationally recognised approach to achieving a safe road transport system through safe interactions of people, vehicles and the road environment.
“To achieve a Safe System, speed must be managed so that human tolerance to serious injury is not exceeded,” said Dr Doecke.
“A speed limit that aligns with the Safe System would be one that, if adhered to, would result in the risk of death or serious injury in the event of a crash being negligible – in our study, the fatal crash rate was non-negligible at all speed limits.”
Furthermore, the study, published in the journal Traffic Injury Prevention, revealed fatal crash rates generally increased as speed limits increased.
“This suggests that the speed limits in Australia do not sufficiently account for the different levels of risk found on the road network,” said Dr Doecke.
“In an 80 km/h zone, the risk of a crash being fatal is three times higher than in a 50 km/h zone and, in a 100 km/h zone, it is more than six times that of a 50 km/h zone.”
Dr Doecke said the risk of a crash being fatal on a 110 km/h road in South Australia is more than 12 times higher than in a 50 km/h zone.
“We found lowering the fatal crash rate in Australia could be achieved through improvements to the roads, improvements in the crash protection of vehicles, and the lowering of speed limits, or a combination of these approaches,” said Dr Doecke.
“That the highest fatal crash rate was in 100 km/h zones raises concerns about the suitability of the default rural speed limit found in Australian Road Rules model law, and adopted by NSW and SA.
“A default rural speed limit saves governments from having signed speed limits across their entire road network.
“However, a default limit may encourage the application of a speed limit without consideration of the safety of the road.
“The results suggest that a default limit is too high for a substantial proportion of the roads to which it is applied.”