Drivers in Victoria will face big fines if they do not slow to 40 kilometres per hour when passing emergency vehicles with flashing lights or sirens that have stopped on the roadside under changes to be introduced next month.

From July 1, people who break the new road rule could be forced to pay a $277 on-the-spot fine or a court-imposed penalty of up to $793.

They will not lose demerit points.

The State Government said the speed limit would help protect police and paramedics who were in danger of being hurt or killed on the job by speeding cars and trucks.

A recent survey found one-fifth of emergency workers reported having several close calls while helping people on the roadside in the last three years.

Roads Minister Luke Donnellan said police would have the discretion to warn or fine a driver, but he hoped the number of motorists caught speeding past accidents would be "minimal".

"Emergency services workers are telling us that they feel in danger while they're doing their job," he said.

"Sometimes it will be difficult to enforce but it's about getting the community to think about safety first."

Police Association secretary Wayne Gatt said officers were more likely to target people who blatantly sped past emergency service workers.

The rule will apply to Victoria Police, Ambulance Victoria, Metropolitan Fire Brigade, Country Fire Authority and State Emergency Service vehicles.