A truck driver has died after being struck by his own vehicle in a tragic incident on a major Brisbane motorway, sparking peak-hour traffic chaos and significant delays.

Queensland Ambulance said they were called to a crash on the Gateway Mwy northbound at Old Cleveland Rd on ramp in Belmont about 5.10am on Tuesday.

Initial investigations indicate the man had pulled over to inspect his truck when it rolled over him, police said.

Know the news with the 7NEWS app: Download today

He sustained critical injuries and was declared dead at the scene.

Queensland Police are now appealing for witnesses or anyone with dashcam or CCTV footage from the area at the time of the crash to come forward.

The incident forced the closure of two northbound lanes, causing significant delays for morning commuters.

Motorists were urged to avoid the area, with traffic stretching back more than 10km and delays exceeding 90 minutes.