Victoria's peak motoring body has cast doubt on new road rules requiring drivers to slow down to 40km/h when passing emergency vehicles, calling for an urgent review of the new policy.

The RACV revealed on Tuesday it had raised concerns with the state government about the practicality of slowing down from speeds of up to 110km/h on country roads and freeways.

The new laws require all motorists to slow to 40km/h when passing stationary or slow-moving emergency vehicles displaying lights or sirens, or risk a $277 fine.

But RACV roads and traffic manager Dave Jones said he feared there would be safety implications for other road users, and said there should have been a longer education period before the laws were introduced.

"In some situations, for example high-speed country roads that have got hills, they're undulating roads and sharp bends," he told radio station 3AW.

"It may be very difficult for someone to see the flashing emergency vehicles' lights far enough in advance so they can slow down to 40 in time. And if they do manage to slam on the anchors ... will any vehicle behind them be able to do it?"

Mr Jones told Fairfax Media that VicRoads needed to better explain the new road rules to ensure motorists understood.

Victorian Transport Association CEO Peter Anderson said heavy vehicles should be afforded special consideration because of their size and weight.

"Trucks carrying loads and travelling at speed on freeways, down hills and around corners can't just abruptly slow down, and attempts to do so could be unsafe and cause more harm than good," he said.

The changes, which come into effect on July 1, were introduced to reduce the number of deaths and injuries among roadside emergency workers.

Associate Professor Stuart Newstead of Monash University's accident research centre, said educating heavy-vehicle drivers to safely slow down at emergency scenes was critical to the policy's success.

"The intent of the changes is very good but we need to be educating motorists extensively on the new rules ... a small segment on television or an article in the newspaper is not enough. There needs to be major publicity about it," Associate Professor Newstead said.

"This is particularly important for heavy-vehicle drivers because if they don't know to slow down they can take a lot of people out with them which can obviously have very serious outcomes for everyone involved."

The sweeping changes were announced by Roads Minister Luke Donnellan on Monday after a survey found almost one-in-five emergency service workers said they'd had four or more near misses on roadsides over the past three years.

Mr Donnellan said there would be an extensive campaign to ensure road users were aware of the change.

The rule will apply to police, ambulance, fire, SES and VicRoads vehicles on all types of roads, including all lanes on freeways.

No demerit points will apply to the rule, but the maximum court penalty will be $793.

With Tom Cowie, Robyn Grace

- The Age