One of the responsibilities of designing something is testing it, which a man was doing with a roller coaster. He was rather proud of this new design, in fact he allowed someone else to ride with him. The designer knew the ride would only take three minutes.
The designer would only last for one.
The coaster made a clacking sound as the car went up the first, and incidentally the highest, hill. Once he got to the very top of the hill, his friend pushed him out of the car.