How do parking sensors work?

It’s so easy to do your car some serious damage when parking, but thankfully this technology can make us all parking masters

Parking sensors are now must-have technology. They enable us all to park ever-larger cars with expert finesse and avoid scrapes that can cost hundreds to repair. The most familiar type use ultrasonic technology – just like bats do!

When activated, these fire out high-frequency signals from a series of round sensors (usually four) attached to the bumper. When physical objects are detected within a set range, they will alert the driver via a visual or audible signal. Manufacturers programme the range of these signals within the logic board of the sensors; they can therefore be calibrated so the driver has an indication of how far away the object is. Usually, widely spaced bleeps are issued. As the car gets closer to the object, the pause between these shortens, until a continuous tone is heard. 

The alternative sensors are electromagnetic. These comprise a magnetic strip on the inside of the bumper – it is ‘invisible’ technology so is more aesthetically pleasing. When activated, a magnetic field is generated; from this, an elliptical magnetic field is sent out by a control unit. When something enters its range, the voltage in the control unit increases. The rate of this change is converted into a calibrated audible signal.

How cars can take over the parking process

1. Smart sense

Parking systems use a car’s ultrasonic sensors in a smart way. Below a set speed, the two outside ultrasonic sensors on the bumpers scan sideways and measure sudden changes in distance that indicate the presence of a space

2. Parking algorithm

Algorithms compare the length of the space with the known length of the car, plus the required ‘manoeuvring space’.

3. The car steers itself

Some cars are fitted with electrically assisted power steering, so the motor can ‘take over’ the steering process. Engineers have defined the requisite steering movements to parallel-park, and stored these in the software

4. Take out the guesswork

Once the system is engaged, it will steer in exactly the right way to perfectly park the car next to the kerb – there is no guesswork, as the steering profile of how to park that exact model has already been calculated.

5. Driver remains in control

The driver still controls brakes, throttle and gears for safety. The system still uses parking sensors in a traditional sense for distance measurement, too – the tolerances are no different as the movement of the car is still under the driver’s control.


 This article was originally published in How It Works issue 11


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