He suspected the driver had “done a runner”.
“All of a sudden, the door on the driver’s side flung open and there’s heaps of smoke coming out of the car,” Hales told the Herald.
“I drive up behind it thinking, ‘man, there’s someone in there hurt or something’. I look in and there’s no one in there. And here’s the car still going along the motorway.
“I think, ‘flipping heck, this isn’t good. There’s no one in the car and the car’s still going’.”
Hales said he raced ahead of the driverless car and pulled over to try to stop the SUV, which “wasn’t going too fast”.
“I run back down the motorway towards the car and try and push it to stop, and it wouldn’t stop.
“So I let the car go past, and then I run up beside the car … and I jumped in the car, because the door was open, and pulled the handbrake on.”
A witness stopped the car by jumping into the vehicle and pulling on its handbrake.
He said the SUV travelled about 200m-300m before he managed to stop it.
Police and fire crews arrived shortly after.
“It was bizarre … I still can’t believe it happened to be honest.”
Hato Hone St John said three patients were assessed at the scene, with no one taken to hospital.
Police have been approached for comment.