Park (P) – This selection
mechanically locks the transmission, restricting the car from
moving in any direction. A parking
pawl prevents the transmission, and therefore the vehicle,
from moving (although the vehicle's non-drive wheels may still spin
freely). For this reason, it is recommended to use the hand brake (or
parking brake) because this actually locks the (in most cases,
rear) wheels and prevents them from moving. This also increases the
life of the transmission and the park pin mechanism, because when
parking on an incline with the transmission in park without the
parking brake engaged will cause undue stress on the parking pin.
An efficiently-adjusted hand brake should also prevent the car from
moving if a worn selector accidentally drops into Reverse gear
during early morning fast-idle engine warmups.