Roller coaster wheels are designed to prevent the cars from flipping off the track. They secure the train to the track while it travels through fancy loops and twists. When you go upside down on a roller coaster, inertia keeps you from falling out. This resistance to a change in motion is stronger than gravity.

Roller coaster designers utilize a "redundant safety" approach to ensure riders stay secured. The primary tools are physical restraints, which fall into two main categories: Lap Bars, which secure the rider at the waist, and Over-the-Shoulder Restraints (OTSRs), which provide a five-point style of security. These are often supplemented by a secondary seatbelt that acts as a backup. Beyond the bars themselves, the seat bucket design is crucial; seats are ergonomically shaped to use the ride's own G-forces to "pin" the rider into the chair during inversions. Modern coasters in 2026 also use sophisticated hydraulic locking systems that allow for an infinite number of positions to fit different body sizes precisely, and "zero-G rolls" are mathematically calculated so that centripetal force keeps the rider's body moving with the car even if the restraints were loose.