Editing Automatic transmission (section)

====P–R–N–D–L positions====
Most cars use a "P–R–N–D–L" layout for the gear selector, which consists of the following positions:<ref>{{cite web |url=https://www.ecfr.gov/current/title-49/subtitle-B/chapter-V/part-571/subpart-B/section-571.102 |title=Standard No. 102; Transmission shift position sequence |website=Code of Federal Regulations |at=Title 49 § 571.102 |access-date=August 16, 2023}}</ref>

* '''Park''' (''P''): This position disengages the transmission from the engine (as with the ''neutral'' position), and a [[parking pawl]] mechanically locks the output shaft of the transmission. This prevents the driven wheels from rotating to prevent the vehicle from moving. The use of the [[hand brake]] (''parking brake'') is also recommended when parking on slopes, since this provides greater protection from the vehicle moving. The ''park'' position is omitted on buses/coaches/tractors, which must instead be placed in ''neutral'' with the air-operated parking brakes set. Some early passenger car automatics, such as the pre-1960 [[Chrysler]] cars and the [[Corvair Powerglide]], did not have the ''park'' feature at all. These cars were started in ''neutral'' and required the driver to apply a parking brake when parked. The original [[Hydra-Matic]] from GM instead engaged a parking pawl when placed in ''reverse'' with the engine off, thus dispensing with a ''park'' position until the adoption of the Controlled Coupling Hydra-Matic in 1956.<br>The ''park'' position usually includes a lockout function (such as a button on the side of the gear selector or requiring that the brake pedal be pressed) which prevents the transmission from being accidentally shifted from ''park'' into other gear selector positions. Many cars also prevent the engine from being started when the selector is in any position other than ''park'' or ''neutral'' (often in combination with requiring the brake pedal to be pressed).
* '''Reverse''' (''R''): This position engages ''reverse'' gear, so that the vehicle drives in a backwards direction.<ref>{{cite web|url=https://www.merriam-webster.com/dictionary/reverse%20gear |title=Reverse Gear |publisher=Merriam-webster.com |access-date=2018-06-24}}</ref> It also operates the reversing lights and on some vehicles can activate other functions including [[parking sensor]]s, [[backup camera]]s and reversing beepers (to warn pedestrians).<br>Some modern transmissions have a mechanism that will prevent shifting into the ''reverse'' position when the vehicle is moving forward, often using a switch on the brake pedal or electronic transmission controls that monitor the vehicle speed.
* '''Neutral''' (''N''): This position disengages the transmission from the engine, allowing the vehicle to move regardless of the engine's speed. Prolonged movement of the vehicle in ''neutral'' with the engine off at significant speeds ("coasting") can damage some automatic transmissions, since the lubrication pump is often powered by the input side of the transmission and is therefore not running when the transmission is in ''neutral''. The vehicle may be started in ''neutral'' as well as ''park''.
* '''Drive''' (''D''): This position is the normal mode for driving forwards. It allows the transmission to engage the full range of available forward gear ratios.
*'''Low''' (''L''): This position provides for engine braking on steep hills. It also provides for a lower gear ratio for starting out when heavily loaded.

Some automatic transmissions, especially by [[General Motors]] from 1940 to 1964, used a layout with ''reverse'' as the bottom position (e.g. N–D–L–R or P–N–D–L–R).<ref>{{cite news |url=https://www.thestar.com/autos/2016/11/12/prndl-why-mess-with-it.html |title=PRNDL — why mess with it? |work=Toronto Star |first=Jim |last=Kenzie |date=November 12, 2016 |access-date=August 16, 2023}}</ref>{{failed verification |date=August 2023}}