A new RMIT University study has found that reducing residential speed limits from 50km/h to 30km/h could dramatically improve safety for bicycle riders — and make suburban streets safer for all road users — with minimal impact on car travel times.
The findings arrive as Victoria introduces new legislation allowing councils to propose 30km/h limits in local streets and school zones.
Researchers at RMIT’s Centre for Urban Research modelled traffic conditions across Greater Melbourne, rating every road for “traffic stress” based on factors such as speed limits, traffic volumes and the presence of cycling infrastructure. The results showed that reducing local speed limits from 50km/h to 30km/h cut cyclists’ exposure to high-stress roads by 30%, while more than doubling the proportion of a typical bicycle trip spent on low-stress streets — from just over one-third to more than two-thirds.
Study lead author Dr Afshin Jafari said the results show that slowing down traffic in local streets has a major impact on safety, with only a small trade-off for drivers.
“Most trips should use residential streets only at the start and finish, so 30kph rather than 50kph on those short sections makes little difference,” Jafari said.
“Slowing traffic makes bicycle riding less stressful, encouraging more people to choose bikes as a safe and viable mode of transport.”
The study found that the average short car trip would increase by about one minute when residential limits were reduced to 30km/h — a small price to pay, Jafari said, for safer and more liveable neighbourhoods.
He described the measure as a “practical, low-cost way to improve safety”, particularly compared with more expensive infrastructure solutions.
“Installing physical barriers on every local street would be ideal, but it’s expensive and slow,” he said.
“Slowing down vehicles is a cheap and effective way to improve safety while we wait for longer-term infrastructure upgrades.”
RMIT’s modelling also showed that lower limits could encourage motorists to stick to main roads rather than “rat-running” through residential areas, helping to reduce traffic noise and improve safety for children and pedestrians.
“This should also create safer streets for our kids,” Jafari said.
While cycling is often associated with inner-city commuters, the research highlights that outer suburbs stand to benefit most from reduced speed limits.
“Outer suburban streets often don’t even have footpaths, let alone other infrastructure to separate bicycle riders and pedestrians from motorists,” Jafari said.
With local councils now able to apply for lower residential speed limits, the RMIT study offers a data-driven case for cities and suburbs across Australia to follow suit — creating calmer, safer neighbourhoods that encourage active transport without significantly affecting travel times.
