Parking sensors

Parking sensors are proximity sensors for road vehicles which can alert the driver to unseen obstacles during parking manoeuvres.

The ultrasonic sensors are currently available in several brands of cars, with a variety of brand names such as Parktronic and Parking Aid. Some systems are also available as additional upgrade kits for later installation.

Description
Parking sensor systems use ultrasonic proximity detectors embedded in the front and/or rear bumpers, to measure the distances to nearby objects at low level. The sensors measure the time taken for each sound pulse to be reflected back to the receiver.

Depending on the speed of the vehicle and the distance to the obstacle, the system will warn the driver by visual and/or audible means about the risk of collision. The feedback to the driver will generally indicate the direction and proximity of the obstacle. Warnings are deactivated when the vehicle exceeds a certain speed, and can be switched off for situations such as stop-and-go traffic.

Audible feedback
The most common form of feedback to the driver in a car with parking sensors is audible "beeps" and/or tones. Generally, the frequency of the beep indicates distance from an obstruction, with the beeps becoming faster the closer the vehicle moves to an object. A continuous tone may be heard when the vehicle is extremely close, often warning a driver to stop immediately to avoid collision.

Visual feedback
Some systems use visual aids as well as or instead of audible tones, such as LED or LCD readouts to indicate distance from an object. The direction and distance to the obstacle is indicated by the location and strength of the warning symbols.

Shortcomings
Since the system relies on the reflection of sound waves, it may not detect some items that are not flat or large enough to reflect sound, for example a narrow pole or a longitudinal object pointed directly at the vehicle.