Respect the Forces

Dynamic amusement ride

Acceleration puts the thrill in thrill rides

Amusement rides thrill us by accelerating our bodies. Each curve, drop, loop, launch, or brake alters the rider's state of being, triggering inertial resistance -- the feeling that your body is headed in one direction while the ride is pulling you somewhere else. That's the "illusion of danger" that makes amusement rides exciting.

Safety issues related to acceleration

If both the ride and the rider's body are well-designed and well-maintained, and if the rider's body is well-supported and restrained by the containment system, then the physics end of the safety equation is satisfied. A flaw in a critical component (e.g., the ride track, braking system, rider's back/brain/cardiovascular system), or poor fit between rider and restraint, can be the trigger point for an accident.

Anyone who's spent time at amusement parks or carnivals knows that the quality and quantity of motion produced by different amusement rides varies widely. Some of the newer steel coasters offer a smooth, sweeping, exhilarating swooooosh of a ride, sending your body through seemingly impossible elevations and angles. Older wooden coasters can rattle your teeth and bruise your butt. Computer-controlled rides can simulate the jerky thrills of off-road jeep racing. Human centrifuges create the acceleration of a space launch for millions of armchair astronauts. Spinning carnival rides can literally pin you to the wall or, alternatively, send smaller riders sliding across the seat through a combination of rapid changes in direction and unfitted restraints.

Each thrill ride design offers a different experience to patrons, and each new experience reshuffles the biodynamic equation. Amusement rides are designed for the masses. That means they're generally safe for most people, but it also means their generic design may put some vulnerable individuals at higher risk for accidents or injury on some rides.

Patron restraint and containment

If a rider's body is not well-enough supported or well-enough restrained by the ride's containment system, he or she can be propelled out of the ride by the vehicle acceleration. This is a statistically rare occurrence, but each year riders are seriously hurt and sometimes killed this way. The most common causes of ejection are:

  • Poor fit between ride and rider - This phenomenon almost exclusively involves young children, but obese riders may be at risk on some highly dynamic rides with lap-only restraints.
  • Equipment failure or operator error - The latches on restraints sometimes fail. Ride attendants sometimes forget to latch and double-check each rider's restraints before starting the ride. This doesn't always lead to patron ejection, but it can.
  • Patron error or misconduct - Patrons can put themselves at risk by unlatching their restraint, standing up or turning around in their seat. Sometimes this is done deliberately to increase the thrill factor. Sometimes the motivation is more benign (a rider turns to wave or take a photo, a young child becomes frightened and tries to change position or get off the ride). Either way, this is a very dangerous thing to do. The forces of motion are immutable. If you or your child moves into the wrong position at the wrong moment -- whether innocently or through deliberate horseplay -- the ride may toss you out.

The effects of acceleration can also result in less extreme accidents, such as patrons hitting against something within the vehicle (e.g., the seat back, rigid restraint, or another rider). This is one of the most commonly reported types of accidental injury on amusement rides, accounting for one quarter of roller coaster injuries. Some of these accidents can be prevented if patrons brace themselves effectively against the ride accelerations.

Physiological and psychological effects of acceleration

Speeding, spinning vehicles and rapid changes of direction can apply significant stresses to the human body. Human tolerance to acceleration depends on many factors, including:

  • Magnitude, direction, rate of onset, and duration of the acceleration stress
  • Differences in individual physiology
  • Psychological reaction (i.e., the fear factor)

Human beings are the most complex and unpredictable component in ride design. For more information about physical and psychological reactions to amusement ride acceleration, visit the links below.

Related Safety Tips

Upside down on a roller coaster
Wild Rides
Fast Cars and Wild Rides: Whiplash, Headbanging, and Sqeezeplays.
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Containment and Restraint
Containment and restraint can be affected by patron size, position, and behavior, as well as acceleration.
Dynamic amusement ride
Physiological Effects of Acceleration
Factors that may affect your tolerance to amusement ride acceleration.