Car catches on fire on freeway

A car has caught fire on Perth's Kwinana Freeway, causing traffic chaos.

Traffic stretched back 19 kilometres after the northbound crash about 6am this morning.

Witnesses say the driver of the Holden Commodore was speeding when he hit a ute travelling in front.

The car smashed into a freeway barrier, and burst into flames.

"It literally came across the bridge there, heard like screeching. Turned around and the Commodore has come around too fast on the bend there, and he's just cleaned up the poor guy in the ute, that's just driving along the road," said Brendan Brisbane.

The Kwinana Freeway was down to just one lane near the Leach Highway exit, with delays extending back to the Russell Road exit.

Trains on the Mandurah and Joondalup lines were also delayed, forced to stop after the car caught fire.

The driver of the burning car was treated for shock at the scene.

The driver of the ute wasn't injured.

All three lanes of the Kwinana Freeway have now opened.