The 40km/h zones were trialled for a year, requiring motorists to slow down around car crash scenes and roadside incidents to protect emergency workers.

However, the 40 km/h zones will now only apply to roads with a speed limit of 80km/h. Drivers will only have to slow to a "speed that is reasonable for the circumstances" on faster roads.

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Lucknow Rural Fire Service captain Mick Bloomfield, who campaigned for the changes, said drivers had stopped slowing down at emergency scenes.

VIDEO: Near miss at emergency scene

Mr Bloomfield said about 90 per cent of drivers had obeyed the 40km/h zone during the trial.

"No one will slow down now. They are putting the lives of RFS NSW [workers], ambulance [crews] and tow truck drivers at risk," he said.

"The 40km/h law should have been left where it was.

"Unless there are laws to force drivers to slow down they will not."

Mr Bloomfield said the government was ignoring work safety laws.

"Your employer, in our case the NSW government, has to provide you with a safe work place or made as safe as possible, these laws do not do this," he said.

The Centre for Road Safety evaluation of the trial found there was strong social media feedback opposing the 40 km/h zones.

Mr Bloomfield said motorists opposed to the zones should see it from the emergency workers' position.

He said the Lucknow crew had attended 28 roadside calls, including eight crashes, this year.

"The RFS has the right, under the law, to close roads if it is dangerous for our members. I am sure this will frustrate drivers more than slowing down," he said.