This system uses four ultrasonic sensors located in the rear bumper, activated when the ignition is switched on and reverse gear has been selected. A short tone will sound to indicate the system's readiness. As the driver reverses, the sensors measure the distance to the closest obstacle behind and immediately to the side of the vehicle's rear end.

When an object is detected in the 'cone' of any of the ultrasonic beams, the driver hears a series of tones from a dedicated speaker located in the rear pillar trim: the faster the tone repeat, the nearer the object. Once the object is within around 30cm of the rear of the car, the tone sounds continuously to warn the driver of impending impact.

Whilst the system is a very useful aid for drivers, the effectiveness of the sensors may be limited in certain circumstances:

• the sensors are not kept clean

• if an object is above or below the sensor beam cone

• from ultrasonic waves, heavy rain or disruptive reflection

Any driver is urged to use the system as an auxiliary assistant to the precautions that they would normally use when reversing.

A simple aid to help avoid the inherent risks of reversing

• Simple and easy to use audible warning system

• Minimises the risk of a collision and a costly repair bill