Low tyre pressure warning: Tyre pressure has been identified as a contributing factor to fatal crashes involving SUVs in the US two years ago which led to the recall of thousands of Firestone tyres and Ford SUVs.
Combined with the arrival on the market of run-flat tyres, cars are likely to be fitted with low tyre pressure warning systems as standard in the future.
The problem with run-flat tyres is that motorists might not notice they have a flat until they're in a bend and they are being overtaken by the back of the car.
The warning system alerts the driver if the pressure in a tyre becomes too low, typically with a light on the instrument panel.
There are two common methods for measuring the pressure. One uses pressure sensors in each wheel to periodically transmit pressure data to a receiver in the vehicle.
If the tyre pressure falls below a set level, a warning light is illuminated. Other systems give readings for the pressure in each tyre so they can be monitored by the driver whenever they wish.
Another system measures wheel speed and uses the difference in speed to detect low pressure. A warning light will alert the driver in about three miles.