Everything Else . As a 1988 article in Science Times by William J. Broad explained, the train's potential energy, gained as a chain drive lifts cars through the earth's gravity to the top of that first drop, has been mostly converted to kinetic energy by the time the ride ends. There are no engines, no motors, just gravity pushing riders along. Since speeding cars have no energy of their own, they can never climb higher than that first hill.
Secondary hills get progressively smaller as the potential energy is used up.
Many rely on the clothoid loop, a teardrop shape that makes it easy to turn people upside down without dropping them. Designers previously had little success with a 360-degree circle. When entering such a circle, a speeding coaster car moves rapidly upward, generating a strong centrifugal force that presses riders into seats with too much energy. The danger at the top is just the opposite. The cars decelerate sharply, and if a car slows too much, gravity can pull riders from their seats while the cars are upside down.