park

Park (P) is a transmission state that mechanically locks the output shaft to prevent vehicle movement. Unlike Neutral, which simply disengages the engine from the wheels, Park applies an internal pawl or spring-loaded latch that catches a toothed ring attached to the transmission's final drive. This creates a mechanical barrier rather than relying on friction alone, making it the only safe position for unattended parking on slopes or in traffic areas.

The locking mechanism typically engages when the shift lever reaches the P detent. In most automatic transmissions, the pawl catches a single large tooth or a series of smaller teeth cast into the differential case or a dedicated parking gear. This design allows drivers to park without engaging the emergency brake, though many vehicles still recommend using both systems on grades. The mechanical lock is what prevents roll-off if hydraulic pressure is lost, making it fundamentally different from all other gear positions.

Park cannot be selected while the vehicle is moving. Modern vehicles use shift interlocks, solenoids, and electronic controls to prevent this; attempting to shift into P at speed can damage the pawl or transmission. The shift lever must be fully depressed and held in the P detent for a moment to ensure full engagement. On vehicles with push-button shifters or electronic shift-by-wire systems, software enforces this rule before Park becomes available.

Wear on the parking pawl is a common automatic transmission failure. Repeated hard parking on hills, using Park instead of the emergency brake, or sudden jolts while parked can crack or bend the pawl or strip its teeth. Rebuilding an automatic transmission is often necessary if the parking mechanism fails because this single component cannot usually be serviced separately. Preventive use of the parking brake is cheap insurance against this expensive repair.

The symbol P on gear selectors derives from the first automatic transmissions of the 1940s, where it appeared alongside R, N, and D. Early automatics in luxury cars pioneered the feature because they freed drivers from manually managing neutral on hills. The letter convention has remained unchanged for over 75 years and appears on dashboards worldwide, making it one of the most universally recognized automotive symbols despite varying names in different languages.