Western Australia's first point-to-point speed camera, which measures average speed over a distance, is being trialled south of Perth from Monday, but police still do not have the power to fine speeding drivers.

The camera will be located along a 26-kilometre stretch of Forrest Highway, near Lake Clifton south of Mandurah.

Seven people have died on that stretch of road in the past six years and 43 others have been injured, Roads Safety Minister Liza Harvey said.

She said the aim was to catch motorists for deliberately speeding over distance, rather than an inadvertent lapse in attention, but conceded police do not have the power to issue fines or lay charges at this stage.

The Government is hoping to have legislation passed in Parliament by the end of the year to allow police to take action against those caught on the point-to-point cameras, Mrs Harvey said.

She also said she would like to see point to point cameras introduced to several other locations once the trial was completed.

Country WA gets first fixed speed cameras

She also announced three fixed speed cameras would be installed on country roads for the first time in a bid to reduce the "horrific" road toll in regional areas.

Two cameras will be located on Great Eastern Highway, one in Wundowie and another in Northam, and the third will be on Indian Ocean Drive in Gabbadah, north of Perth.

Mrs Harvey said the locations were notorious black spots, with 100 crashes along the stretch of Great Eastern Highway between 2011 and 2015, resulting in six deaths and 34 people injuries, while 15 people were injured in 33 crashes along Indian Ocean Road in the same period.

"We are really responding to what has been a horrific road toll out in regional areas and one of the main causes of fatal and serious injury crashes is excess speed," she said.

"We know where we install the fixed speed cameras we get 60 per cent of motorists reduce their speed, so that's a significant outcome."

The cameras will be operational by December.

WA's road toll for the year stands at 154, with 95 of those deaths on country roads.