"I didn't see it until the glass smashed all over my face," he said.
"I jumped out and turned him on his side. I called out to my mate and got him to call an ambulance."
Mr Nepson said he didn't hear anything until he felt something hit his driver's door. "The front wheel was in front of my face and he was lying there."
He said he spoke to the rider of the bike who was conscious at the time.
Mr Nepson was not injured apart from a few cuts.
Police would also like to speak with anybody who witnessed the crash or saw the vehicles travelling along No 2 Line shortly before the crash.
Information can be passed to the District Command Centre on 06 351 2535.