The car of the future will be safer but at a cost - both in terms of hard cash and the privacy of motorists.

Within five years cars will be able to have built-in radar that can sense other vehicles, children or pets in the blind spots behind the car.

But privacy advocates object to another innovation being introduced in European cars: "black box" systems that record what the car - and its driver - did in the moments leading up to a crash.

"It's Orwellian," said Simon Davies, director of the civil liberties group Privacy International. "If you owned a car with one in, you would have to release the data from a crash or else your insurance company wouldn't pay up. It's a dangerous jump to take."

Other technology in development will make cars harder to steer towards obstacles to either side. Scientists are also looking at "drive-by-wire" aircraft systems. which would disconnect the steering wheel from the car's wheels.

Peter Bell, business manager of the automotive unit at Cambridge Consultants, said the extra cost of such systems could be just €300 (£210), making it feasible for car companies to build them in without huge cost. "Putting short-range radar into the back and sides of the car would take about 18 months. Some time after that you could have longer-range radar built into the front of the car, which would warn about or even avoid crashes."

The "blind spot" radar is seen as the most urgent need, because small children standing behind people carriers in, say, a driveway, are not always visible to the driver.

Some cars already have ultrasonic sensors in the back bumper but these cannot distinguish objects' size or height.

Prototypes project what is behind the car on to a screen in the back of the car - although it could be shown on a rear-view mirror, Mr Bell said.

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