POLICE will install WA's first fixed freeway speed camera on Mitchell Freeway as they prepare for a Christmas-New Year road blitz.

Senior officers this week would not disclose where on the 30km northern freeway it would be placed, or whether it would be on northbound or southbound lanes.

But Acting Police Minister John Day said more fixed camera locations would be rolled out if the trial was a success.

WA Police have bought several German-made metal cabinets to house permanent speed cameras. For now, just one of them will be fitted out, as part of a trial starting next month.

Mr Day said no new cameras had been bought; instead, one of the 23 existing demountable cameras would be installed in the cabinet during the trial.

"Speed cameras operate on freeway roadsides already, either in vehicles or on tripods, and this is simply another method of deployment intended to improve road safety," Mr Day said.

He said signs warning of the camera's position would also be installed, even though it was not required by legislation.

Monash University road safety researcher Max Cameron has suggested previously that point-to-point speed cameras to target speeding drivers over long stretches should be installed on more than 3000km of WA's roads, including sections of the Kwinana and Mitchell freeways.

Acting Assistant Commissioner for specialist enforcement and operations Michelle Fyfe said the effectiveness of the fixed freeway speed camera would be assessed before a decision was made to install more of them.

"This trial is a direct result of research conducted specifically on Perth roads," Mrs Fyfe said.

She would not say how many cabinets had been bought.

Opposition police spokeswoman Margaret Quirk cautiously welcomed the fixed freeway cameras, but questioned whether the camera locations were based at problem areas and if they would improve road safety.

"It's clear there's a speeding problem on freeways, but whether that translates to fatalities and serious injuries will be borne out in the results of the trial," she said.

RAC head of member advocacy Matt Brown said a survey of members showed 59 per cent of motorists favoured fixed speed cameras on freeways, but acknowledged the devices needed to be part of a broader speed enforcement program across the entire state.

He said WA lagged behind other states in the introduction of fixed speed cameras, with fixed cameras already in place on freeways in most major cities across the eastern states.

WA Police Union president Russell Armstrong said the fixed freeway camera trial would complement additional motorcycle patrols on Perth's freeways to slow leadfoot drivers and save lives.

coxn@sundaytimes.newsltd.com.au