The Park Pilot system assists the driver when they are parking their vehicle. Audible signals let the driver know how much room there is behind the vehicle and on some models how much space there is in front of the vehicle as well. The frequency of the signal tones increase as the vehicle draws closer to the obstacle. Once the distance to the object drops below 30cm a continuous tone sounds. Depending on the model of navigation systems, the distance to any obstacles is indicated visually in the display.