Driver speaking to police after WA crash

A WA driver has come forward after an object from his vehicle smashed into the front of another car, leaving a man with serious injuries.

Police say the injured man was driving behind a white four-wheel-drive towing a large boat on the Bussell Highway near Ludlow on Friday afternoon when the incident occurred.

The man, who is believed to be in his 40's, was flown to Royal Perth Hospital with serious injuries while a female passenger and two children in the car were unharmed.

The man believed to be driving the white 4WD has made contact with police.