A man's dashcam has caught the moment a driver lost control on a Perth freeway and decided to take it out on the moving traffic - using his head.

He can be seen headbutting several moving cars, smashing windows and throwing himself head first through the windscreens of others.

The shocking incident happened after the man crashed his Mazda ute into an unattended Volkswagen which was parked in the emergency lane of Kwinana Freeway in Perth.

Witnesses report the agitated man got out of his vehicle and ran into the oncoming traffic, jumping on the bonnets of some cars before smashing everything in sight.

The dramatic outburst forced traffic to stop and caused a major jam on the city highway. Eye witnesses took to social media to report the incident, with one posting the dashcam footage of the man on YouTube. A police spokeswoman said inquiries are continuing into whether alcohol or drugs were involved.

The man is being assessed at Fremantle hospital.