A Ford Kuga burst into flames near the London Road offramp on the N3 near Alexandra in Sandton on Monday.
"One of the guys from Ford had taken the car for a test drive‚" said Captain Granville Meyer.
"The car suddenly set alight on its own‚" he said.
A motorist‚ Daren Grusin‚ supplied the publication with pictures of the fiery vehicle.
"I was driving past when I saw the car there‚" he said.
Another person posted a video of the burning car.