Wen Ko, an engineer at Case Western Reserve University in Cleveland, Ohio, says current instruments that tell drivers the condition of their tyres are expensive and unreliable.

With a team at Goodyear, Ko has designed and patented the device using microscopic components known as microelectromechanical systems (Mems). He says these are cheap, reliable and last up 12 years - the same as a tyre.

Goodyear has successfully tested the sensors in truck tyres but refuses to reveal when the device will go on sale. Motoring organisations have welcomed the invention, saying motorists rarely check their tyres. But they are warning drivers not to rely on the technology.

A spokesman for the AA said: "It does sound like a very smart device and is good news for the future. But there is still no substitute for actually getting down on your knees and checking the tread and condition of your tyre."

Pressure changes

The pressure sensor is a tiny capacitor made from two parallel silicon plates.

The thinner top plate changes shape if the air pressure changes. This produces a change in the capacitance of the device.

The temperature sensor is made from semiconductors that change their resistance as their temperature changes. The hotter the sensor, the closer it is to the tyre surface and the more worn the tyre.

The sensors, together with a transponder, are incorporated into the wall of the tyre during manufacture. To find out its temperature or pressure, a radio signal is sent out by a transmitter built into a vehicle or a handheld scanner.

The incoming signal provides enough power for the transponder to run the sensors and beam back the tyre's vital statistics.