Steering is the term for the collection of components, linkages, etc. that allow a car or other vehicle to be turned to follow the desired course of its driver. The most conventional arrangement is to turn the front wheels using a hand-operated steering wheel, which is positioned just in front of the driver. Other arrangements are sometimes found on different types of vehicles, for example a tiller, or rear-wheel steering. Tracked vehicles usually employ differential steering - that is, the tracks are made to move at different speeds, or even in opposite directions, to bring about a change of course.
Most modern cars use rack and pinion steering mechanisms. Older designs often use the recirculating ball type of mechanism, which is still found on trucks and utility vehicles, etc. In a rack and pinion design, the steering wheel turns the pinion via the steering column, which may use universal joints. The rack moves from side to side and applies torque to the kingpins of the steered wheels via a short lever called the steering arm. Ackermann steering geometry is commonly used to allow each wheel to trace the correct path when travelling in a curve.
For safety reasons, all modern cars feature a collapsible steering column, which will collapse in the event of a heavy frontal impact to avoid excessive injuries to the driver. This safety feature first appeared on cars built by General Motors after an extensive and very public lobbying campaign by Ralph Nader.
