On a PRNDL automatic selector, R engages reverse gear. Selecting R makes the transmission transmit power in the direction needed for the vehicle to move backward, subject to the vehicle’s safety controls and operating conditions.
The familiar PRNDL sequence means Park, Reverse, Neutral, Drive, and Low. Reverse is normally positioned between Park and Neutral, although older vehicles and some unusual designs used different layouts. Modern cars commonly prevent a shift into reverse while moving forward, using mechanical lockouts or electronic controls.
Reverse is not simply neutral with the wheels turning the other way. Automatic transmissions use planetary gearsets, clutches, bands, or related mechanisms to create the reverse ratio. Selecting reverse can also activate reversing lights, parking sensors, cameras, and warning beepers.
Drivers sometimes confuse R with a low forward range because both may be used during slow manoeuvres. The distinction is fundamental: R commands backward motion, while L restricts the transmission to lower forward ratios for situations such as steep hills or heavy loads.