Saving lives and creating more livable communities are just two of the reasons given by researchers as to why there should be a nationwide reduction of local speed limits from 50km/h to 40km/h -- pointing to 30km/h limits on roads in Europe as an example.
Marina Alexander and Dr Mark King, from QUT's Centre for Accident Research & Road Safety – Queensland (CARRS-Q) say because there was a default speed limit of 50km/h in built-up areas, unless otherwise signed, this had become the default speed limit for local streets as well as for other roads in built-up areas, such as collector roads and some arterial roads.
"We say 50km/h is too high for local streets, which is why we are seeing 40km/h zones around schools and shopping areas introduced all over the country as local governments respond to public demand for lower speeds," Ms Alexander said.
"Many countries in Europe have introduced 30km/h for local streets and these countries lead the world in road safety outcomes."
Ms Alexander said local streets were typically characterised by their mix of traffic, which included vulnerable or unprotected road users such as pedestrians, cyclists and people on motorised mobility scooters.
"The latest Queensland road crash statistics show a disturbing trend of increased fatalities and serious injuries for pedestrians and cyclists," Ms Alexander said. "If a person in a motor vehicle is involved in a road crash at 50km/h they have a 10 per cent or less chance of being killed. Those are pretty good odds".
However, if an unprotected person, such as a cyclist or pedestrian is involved, their chances of being killed rise to between 50 and 80 per cent.
"Safer vehicles and safer streets are key elements to increasing road safety for motorists but the effect is marginal for vulnerable people who do not necessarily benefit from technical improvements in vehicles or road infrastructure."
Ms Alexander said while a difference of 10km/h had the potential to save lives, it did not necessarily mean slower trips.
"Research has demonstrated in most urban trips under 20 minutes, higher speeds make little difference to travel time and in some cases lower speeds could reduce travel time due to improvements in traffic flow," she said. "But from a safety perspective there are huge gains we can make".
Higher impact speeds lead to the exertion of greater force, and a higher magnitude of injury for an unprotected person. Slower speeds produce less kinetic energy resulting in less serious injuries. Slower speeds also allow for longer reaction times, greater braking distance and a decrease in the likelihood of crashing.
Ms Alexander said speed limit changes in the late 1990s in Queensland, NSW and Victoria from 60km/h to 50km/h saw a reduction in road deaths of 15 per cent.
"It's time to continue this downward trend," she said. "More people are choosing to walk, cycle or use alternative forms of transport instead of driving. This positive change brings with it new demands on the road network. We argue that lowering the speed limit is a fundamental to achieving safer local streets for all people."