Jared Vercoe (26) was driving an Intercity coach south about 4.10pm on Friday when he noticed an item, which he later discovered was a truck's brake caliper, lying on State Highway 1, where a passing lane merged, about 3km north of Orari.
At that moment, a car in the next lane swerved to avoid it, but flicked the caliper up, turning it into a missile headed for Mr Vercoe's head.
"I just thought, 'What the hell is that?' And there was nothing I could do about it. It just came right at me."
He ducked to avoid the caliper, which smashed through the reinforced window, shattered the windscreen, flew over his head and landed in the aisle of the bus, which was carrying 22 passengers.
Mr Vercoe, who was covered in glass, managed to pull the bus over.
With Mr Vercoe in shock, a fellow coach driver who was a passenger on board drove the bus at 30kmh to Orari, where everyone on board was transferred to another coach.
The damaged bus was returned to Christchurch for repair.
Mr Vercoe was dropped off at Timaru Hospital, where glass was cleaned from his ear and a cut on his arm tended to.
Police attended the crash and Ritchies, which owns Intercity, is conducting an internal investigation into what happened.
It was not the first time Mr Vercoe has had bad luck at that spot.
In December, a man died when the car he was driving crashed into the front of Mr Vercoe's bus.
Mr Vercoe and three of his passengers were injured in that crash.
"It's a fine bit of road, but for two freak accidents to happen in the same place, so close together it's ... phew," he said, shaking his head.
However, the incidents have not put him off.
The next day, he was back driving the same route.
