Rollover

Rollover is a type of vehicle accident, where a vehicle turns over on its side or roof. This happens when the centre of mass ends up outside of the vehicle area of contact with the ground defined by its wheels.

The main cause for rolling over is turning too sharply while moving too fast. The force of inertia (acting in the direction opposite to the one it is turning) is combined with the force of gravity (acting downwards). When the combined force as applied to the centre of vehicle's mass falls outside of the rectangle formed by the wheels, the vehicle starts to turn over. A skilled driver may stop the fall by stopping the turn. It is possible to drive the car then on two wheels for some time.

All cars are susceptible to rollovers to various extents. Generally, the higher the centre of mass is located, the higher the vehicle is and the faster it goes, the more likely it is to roll over. SUVs are particularly notorious for rolling over. HMMWVs, on the other hand, are nearly invulnerable to this type of accident. According to anecdotal evidence, however, it can be rolled in very specific circumstances and this was done on purpose twice in the Israeli army. A driver needs to move backwards very fast and then do a sharp turn, and immediately slam the brakes to block the wheels.

Trucks can often roll over when doing sharp turns and trains can roll over after derailing.

Some four wheel drive pickup trucks have reduced steering capacity to prevent rollover. This creates problems with parking and negotiating very sharp curves.

A vehicle may roll over for other reasons, for example when hitting a large obstacle with one of its wheels, when manoeuvring over uneven terrain, etc.

After the rollover the vehicle may end up lying on the side or on the roof, often blocking the doors and complicating the escape for the passengers. Large passenger vehicles such as buses, trams and trolleybuses that have doors on one side only usually have special windows with handles to pull to use the window as an emergency exit or glaziers fixed near the windows for cutting the glass and making an improvised exit in case of a rollover. Some have emergency exits in their roofs.