Parking is similar to driving. To park a vehicle, the player has to stop the vehicle at their desired location and exit. In the different GTA universes, parking mechanics have become slightly more realistic than simply exiting the car.
Parking in 3D Universe games consisted of the player exiting the vehicle at their desired location. When the player leaves the vehicle, the engine will idle and the headlights (if they are on) will remain on. The only way to "perfectly park" is to save a vehicle in a garage. Modifications are available that allow the player to turn the engine off.
In the HD Universe, parking has become more realistic compared to previous games. Players can still stop and go and leave the engine running, but now players can switch the engine off by holding the exit button without releasing it until the character exits. This switches the engine, radio and headlights off. The engine will also shut off if left idle for a long period of time.