An NHTSA study shows that the percentage of people involved in rollover accidents was 21% in 2002, reflecting a 4% increase over 1994, 1995, and 1997. The average yearly percentage of incapacitating and fatal injuries for restrained occupants was determined by analyzing the rollover data obtained from the FARS query and was found to be 35%.

A rollover accident is where a vehicle turns over onto its side or roof. The main cause for rolling over is turning too sharply while moving too fast. When the combination of the force acting in the direction opposite to the one it is turning is combined with gravity or g-force acting downwards is applied to the center of vehicle’s mass falls outside of the rectangle formed by the wheels, the vehicle starts to turn over.

Big vehicles such as such as 18-wheeler tractor-trailer trucks, commercial vans, minivans, and conversion vans can easily rollover. The tendency for a vehicle to rollover is dependent on the g-force required to roll the vehicle. G-force is created when a vehicle negotiates corners.

The following chart illustrates the force required to rollover different kinds of vehicles:

It is almost impossible to generate the required force of 1.3 g for the cars while turning around a corner, whereas it is easy to generate 0.4 g’s required to cause the trucks to rollover. It has been observed that trucks can generate approximately 4 g’s from quick steering maneuvers. A quick maneuver behind the wheel in an attempt to avoid collisions, as well as cornering too fast can generate much larger g-force than the required 0.4 g’s to cause the trucks to rollover.