IT IS everything you are scared of when stuck in a traffic jam on a 100kmh highway.

A dashboard camera has captured the moment a truck carrying a steam-roller is forced to lock up the brakes after realising that traffic in front had come to a stand still.

The truck appears to have sideswiped at least two cars on Sydney's M5 Motorway as it tried to swerve out of the way, a third vehicle bumping into the rear of the truck as it came to a halt.

The woman who posted the video via Dash Cam Owners Australia said she thought none of those in the cars suffered serious injuries.