A truck driver has walked away uninjured from his burning vehicle that crashed on the M1 Pacific Motorway near Maclean in northern New South Wales.

The incident happened soon after six o’clock this morning on a stretch of the highway to the east of the Maclean township. 

Live Traffic said the B-double crashed into a barrier on the M1 and rolled down an embankment on the median strip.

The crash is causing significant delays on the motorway. Southbound lanes are closed, but northbound lanes are now open.

Traffic is backed up for more than 500 metres in both directions and motorists are advised to avoid the area.

Cars are being diverted via the Maclean township, and heavy vehicles are being parked until the road can be cleared.

Police are investigating the circumstances surrounding the crash.

Emergency services remain on the scene and the fire sparked by the crash has now been brought under control.

The Rural Fire Service said the truck was carrying car parts and building supplies, but nothing flammable.