30km/h On Local Streets Safer For Riders, Little Change For Drivers
Lowering speed limits on residential streets from 50km/h to 30km/h would make biking much safer and have minimal impact on vehicle-based travel times.
That’s the key message from new modelling by RMIT University’s Centre for Urban Research.
Victoria has recently made it easier for councils to trial 30km/h limits in school zones and suburban streets. As relevant for all of Australia as it is for Melbourne, the detailed study and findings prove the enormous potential for bike-based transport, particularly if other state governments allow local councils to trial lower speed limits.
Although safety is not a direct aspect of the latest study, it is also a key consideration. A bike rider has just a 45 per cent chance of surviving if they are hit by a car travelling at 45km/h, but at 30km/h that increases to a 90 per cent chance of survival. More can be read on Bicycle Network’s campaigning for low-speed streets here.
Lower Speeds, Minimal Delays
The RMIT study’s lead author is Dr Afshin Jafari, who said that while driving at 30km/h might seem slow, the limit mostly applies to residential streets, so it has little impact on average car trips.
Dr Jafari said the modelling showed the average short local trip only increased by about a minute.
“Most trips should use residential streets only at the start and finish, so 30kph rather than 50kph on those short sections would make little difference,” he said.
“Slowing traffic makes bicycle riding less stressful, encouraging more people to choose bikes as a safe and viable mode of transport,” he added.
What The Study Looked At
Researchers rated every street in Greater Melbourne using Level of Traffic Stress (LTS) – a simple scale from LTS-1 (low stress) to LTS-4 (high stress) based on speed limits, traffic volumes and bike infrastructure. They then modelled tens of thousands of trips under three scenarios:
- Current limits (mostly 50km/h on residential streets)
- 40km/h default on residential streets
- 30km/h default on residential streets
They also ran a transport simulation to see how the lower limits would affect car travel times.
The Findings
- Riding is much less stressful, especially at 30km/h. With a 30km/h limit, the average bike trip spends around 70% of its distance on low-stress (LTS-1–2) streets, up from about 55% today.
- For short trips under 2km, low-stress coverage jumps to around 74%. A 40km/h limit helps too, but 30km/h shifts more riding into the calmest category (LTS-1).
- Driving times barely change. Across the city, average car travel times changed by less than 30 seconds compared with today. Even for local car trips that spend at least half their distance on residential streets, the average increase under 30km/h was about one minute. These are short journeys that many people could switch to walking or riding, especially once streets feel safer.
* Less rat-running. Daily traffic volumes on residential streets declined slightly under lower speed limits, a sign of calmer, more localised traffic.
Why “Low Stress” Matters
People ride more when their route feels calm and predictable. The study’s mode-choice modelling confirmed it: the more high-stress links on a bike route, the less likely someone is to choose the bike.
Lowering residential speeds is a fast, low-cost way to turn everyday connections from homes to schools, shops and stations into LTS-1 streets that feel safe for most riders.
What This Means For Councils (And Residents)
Building protected bike lanes on every street would be the ultimate outcome, but this will take many years and a lot of money. On the other hand, speed management can be rolled out quickly and cheaply, and it works perfectly well alongside longer-term infrastructure plans.
With Victoria now allowing councils to propose 30km/h zones, this research gives local leaders a practical roadmap that includes the ability to –
- Start where it counts: school precincts, shopping strips and residential grids that feed into major bike corridors.
- Target short local trips: the biggest safety gains (and the smallest driver time impacts) are on shorter journeys of two to three kilometres.
- Measure and share results: track crashes, near-misses and mode shift to build community confidence.
What riders will notice
- Calmer links between suburbs: fewer “white-knuckle” gaps between quiet back streets and the bigger cycling corridors.
- More consistent routes: a higher share of your trip on streets that feel safe — not just a protected sector here and there.
- Family-friendly options: school runs and local errands that are safer, easier and more efficient by bike.
What drivers will notice
- Very small time changes: most trips are unchanged; local-street-heavy journeys may take around a minute longer
- Quieter, safer streets: fewer harsh braking moments, easier crossing for pedestrians and riders, and less rat-running.
- Lower operating costs – reduced wear and tear on the vehicle and less fuel.
The Takeaway
RMIT’s modelling is clear: moving residential limits from 50km/h to 30km/h would cut cycling stress by roughly a third. It would also push many more bike trips onto low-stress streets and barely affect car travel times.
And for councils looking for quick wins on safety, health and liveability – without the negative effects of ever-increasing traffic – 30km/h on local streets is a smart, evidence-based step.
The detailed study was recently released by the RMIT Centre for Urban Research and can be read via this link. The authors are Afshin Jafari, Steve Pemberton, Sapan Tiwari, Tayebeh Saghapour, Nikhil Chand, Belen Zapata-Diomedi, and Billie Giles-Corti.
