A car with an automatic transmission selects the correct gear for the driver, using a complex communications system which incorporates information about the speed of the car, whether the driver is accelerating or braking, and the revolutions per minute (RPM) of the engine. All of this work is done without the driver's participation: to go forward, the driver uses a lever to put the car in drive, and to go in reverse, the driver uses the reverse option. Automatics usually also have a park and neutral option, and some have overdrive for high speeds, along with low gears for special driving conditions like snow.
