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Commuters in Melbourne’s northern suburbs could see a 20 per cent increase on their travel time, if speed limits on local roads were reduced to 30km/h. Check how much longer your journey would be.

Commuters driving into the city from Melbourne’s north could see their travel times increase by at least 20 per cent if all local streets across Victoria were reduced to 30km/h.

A Herald Sun analysis of 20 routes from Melbourne's suburbs into the CBD found those coming from Craigieburn would have the most time added to their commutes if Infrastructure Victoria’s 30 year plan to reduce speed limits on 50km/h and 40km/h roads was implemented.

Purely based on current speed zones and not taking into account traffic or red lights, Craigieburn commuters could theoretically make it into the city in 26 minutes.

But this would extend to more than half an hour if limits on Pascoe Vale, Mount Alexander and Flemington roads were reduced to 30km/h.

Likewise drivers coming in from Manor Lakes would have their commutes increased by more than four minutes with the proposed limit change.

In the eastern suburbs people driving in from Box Hill — avoiding the Eastern Freeway — would also have commute times increased by about four minutes.

Shaun Pilmer, who drives from Mernda to Southbank every day, said any extra time on the roads would “make my days even longer”.

He said he was happy slow down to 30km/h in school zones but said lower speeds were “pretty unnecessary” for all residential streets.

But Gardenvale mum Liz Pham said she did not think the proposed change would have too much of an impact on drivers.

“The change will add time to my drive and we will have to leave home a bit earlier,” she said.

“But it makes sense to slow down all the cars on the road.

“With some of the traffic around the school you aren’t able to go much faster than 30km/h anyway.”

Monash University School of Public Health and Preventive Medicine’s Dr Lauren Pearson said reducing speed limits had worked wonders for public safety overseas.

“30km/h speed zones are one of the most cost-effective interventions we can use to enhance the safety and liveability of local streets,” she said.

“Here in Australia, we’re well behind. There are only two areas in Victoria where these have been implemented and they are only on a trial basis.

“We have strong and growing body of evidence for the vast benefits of these interventions, and continued calls for their implementation from not only this report from Infrastructure Victoria, but from a recent road safety parliamentary inquiry, and from the World Health Organization as well.”

Speed limits would be reduced to 30km/h on local roads and school zones as part of an Infrastructure Victoria 2050 plan. Picture: NCA NewsWire / David Crosling

But Associate Professor Ben Beck said while it would lead to safer streets, implementing the change would not be easy.

“Our research has shown that while there is strong support for these speed limits throughout the government, the current speed policy only enables them to be implemented on a trial basis,” he said.

No toll roads or freeways were used in the mathematical exercise, with all routes finishing at Melbourne’s GPO on Elizabeth St.

In response to the reports, Infrastructure Victoria’s Executive Director Mandy Frostick said the reduction in speed limit would not lead to a proportionate increase in travel time.

“”Particularly when driving in local streets in an urban environment, drivers must frequently stop or slow down for intersections, other road users, traffic signals, stop signs, pedestrian crossings, rail crossings, or in busy areas like shopping zones,” she said.

“Therefore, it is inappropriate and misleading to state or assume that a reduction in posted speeds limits from 50 to 30km/h will result in a direct increase in overall travel time.”

SNIPPet 30km traffic speed zone