Four dead in 24 hours on WA roads

Four people have been killed in a horror 24 hours on Western Australia's roads.

In the most recent tragedy, a rescue helicopter was sent to Serpentine, south of Perth, on Tuesday morning where a cement truck, a road train and a car were believed to have collided on Karnup Road.

Police confirmed one driver was killed and another suffered serious injuries.

The crash followed the deaths of a father and son in Kelleberrin on Monday afternoon, after their car was crushed by a semi-trailer while waiting at a level crossing.

As a result, Major Crash Investigation officers charged a 45-year-old NSW man with two counts of dangerous driving causing death.

They will allege he was driving a prime mover with two trailers when he crashed into the Commodore. The 54-year-old father and 21-year-old son from Kalgoorlie died when their car was propelled into bushes and burst into flames.

Meanwhile, police have issued a plea to witnesses to another fatal crash on Monday, which claimed the life of a 19-year-old woman and her unborn child.

Shona Leigh Caley and her partner Alex Riley, 18, were travelling from Perth to their home town of Corrigin about 7.50am, when their blue Mitsubishi Lancer Coupe ploughed off the Brookton Highway and hit a tree.

Mr Riley suffered minor injuries.

Investigators would like to speak to anyone who might have seen the vehicle before the crash.