The two major types of roller coasters are wooden and steel. Features in the wheel design prevent the cars from flipping off the track. Wooden tracks are more inflexible than steel, so usually don't have such complex loops that might flip passengers upside down.

Roller coasters stay securely on the track through a combination of clever mechanical engineering and the fundamental laws of physics. Modern coasters utilize a "three-wheel" system: running wheels sit on top of the rail to support the weight, side-friction wheels hug the sides of the rail to prevent lateral sliding, and up-stop (under-friction) wheels lock onto the bottom of the rail to prevent the car from lifting off during "airtime" or inversions. From a physics perspective, inertia and centripetal acceleration are the primary forces at play. As a coaster goes through a loop, the car's inertia wants to keep it moving in a straight line, which pushes the car outward against the track. The track, in turn, provides a centripetal force that pushes back toward the center of the loop. In 2026, engineers use advanced computer modeling to ensure that the force of the track pushing the car always exceeds the force of gravity at the top of a loop, ensuring that even if the up-stop wheels were to fail, the momentum of the train would keep it pressed firmly against the steel rails.