A leading road trauma researcher says the WA Government lacks the political courage to bring in measures that could cut the State's road toll.

Max Cameron, of Monash University's accident research centre, said speed limits on thousands of kilometres of rural highways across WA needed to be cut from 110km/h to 90km/h, with an 80km/h limit for trucks.

"One of the regrettable things about speed enforcement and speed cameras in particular is that it seems to be a difficult issue for politicians to address," Professor Cameron said yesterday.

"It seems to be an area where there are often very strong negative responses from a vocal minority - it's caused many State governments to be quite weak-kneed about being serious on speed enforcement."

He said existing speed limits were too high for roads that were often poorly maintained and unsafe. "We need to come to grips with the idea that the traditional 110km/h limit on any rural road is just not acceptable," Professor Cameron said.

"When you take into account the travel time and costs of reduced speeds and the enormous road trauma benefits - it tells me a speed of 90km/h by cars on rural undivided roads is the maximum you should be doing."

He said the Government had to begin placing speed cameras in unmarked vehicles and introduce point-to-point speed cameras, which measure the average speed of a vehicle over up to 10km.

The daily publication of speed camera locations should also cease, Professor Cameron said.

"The idea is that a driver should have a fear of being caught anywhere at any time," he said.

"Regrettably, governments don't seem to have the courage to do it."