Changing speed zones have long been an expensive frustration for drivers. Now there are plans to slash speed yet again, this time down to just 30 kilometres an hour.

Melbourne's Lord Mayor Robert Doyle is looking at imposing 30 kilometres per hour speed restrictions on parts of the city centre and in some residential streets.

“It’s a big difference if you have to brake suddenly to avoid a pedestrian or a cyclist,” Lord Mayor Doyle said.

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Dr Bruce Corbin from Monash University's Accident Research Centre agrees.

“A pedestrian struck at 30 kilometres per hour has about a one in ten chance of being killed, whereas at 50 kilometres per hour it’s more like a nine in ten chance of being killed,” he said.

“From a road safety point of view I think we can expect some quite dramatic reductions in risk through that proposition, and I think that's a good thing in terms of the way society is changing.”

With pedestrians comprising fifteen per cent of road deaths, there is a strong argument to lower the current CBD speed limit from 50 kilometres to 30. But would this lead to resentful motorists facing a longer commute through the city?

Brian Negus, General Manager of Public Policy at the RACV thinks the idea is excessive.

“Having 40 kilometre targeted speed limits is practical, but having anything lower is really impractical and would just confuse motorists,” he said

“It’s about the degree of frustration. Why should I actually do this 30 kilometre per hour drive at two in the morning, or ten o’clock at night, when there is no one around? So practicality needs to be a strong indicator of what the speed limit should be.”

It is a debate which will peak the interest of councils and governments around the country, as it already has overseas. “Where these lower speed limits have been trialled, such as London for example, we've seen reductions in motorcyclists deaths of around 40 per cent and pedestrian deaths at a similar level,” Dr Corbin said.

Motorists like Nigel Aiken are cynical about the speed cut proposal. Despite doing lots of freeway driving, his average speed over 60,000 kilometres is just 42 kilometres an hour anyway.

“Just relax and get it back to realistic numbers and let everyone do the right thing,” he said.

Whatever Council decides, VicRoads has the final say, and it believes at this stage a 30 kilometre limit won’t work.

“I think it’s still in discussion, and it needs to be thoroughly considered. We want people to be happy with that, but I think ultimately it will happen. It’s really a matter of the timing,” Dr Corbin concluded.