We can detect a change in efficiency at less than one pint of beer

Dr Dilwyn Marple-Horvat

It is designed to judge whether drivers have had too much to drink and should be allowed to drive.

Its creator, Dr Dilwyn Marple-Horvat of Bristol University, UK, says it has the potential to be installed in cars within a year.

Dr Marple-Horvat told BBC News Online there was a close relationship between drivers' eyes and their hands on the steering wheel.

"We already know that when driving your eyes tend to move to look at the curb just before you start to turn the wheel," he said.

"When drunk, your eyes start to move later and later until eventually, when really drunk, they only move as you hit the bend."

Eye trackers

Dr Marple-Horvat said alcohol affected a region of the brain called the cerebellum, which links parts of the brain that process visual information to parts enabling movement.

His device correlated information from a gadget monitoring steering wheel movement and an in-car eye-tracking system that can tell where eyes are looking through the windscreen.

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The results determined whether a driver has had too much to drink.

"We can detect a change in efficiency at less than one pint of beer," said Dr Marple-Horvat.

The legal limit for driving is 80 mg of alcohol per 100 ml of blood, which roughly equates to one-and-a-half pints of beer, depending on its alcohol content.

Alert police

Dr Marple-Horvat said plans for the device were still at an early stage, but it had potential for a variety of uses.

He said it could simply warn the driver against driving, or act as a black box system which would record the fact that the driver had been warned but continued to drive.

The device could also be linked to the engine to automatically slow the car down, he said. It could even be used to alert police there was a drink-driver on the road.

Whether or not the gadget should be fitted to cars was down to legislators, said Dr Marple-Horvat.

"Personally if I was driving my car and thought I was fine to drive and wasn't, I would prefer to find out before I injured myself or somebody else," he said.

'Don't drive'

But executive director of the RAC Foundation Edmund King expressed some caution.

He said there might be benefits from monitoring the alertness of a driver, but it could dangerous to promote equipment as a drink-driving safety device.

"The simplest and best advice is that if you are drinking, don't drive and if you are driving, don't drink. You shouldn't have to rely on a technological device."

John Stanley, of the Society for Motor Manufacturers and Traders, said the industry always advocated responsible car use.

He said the research might be looked at with interest from a safety point of view, but the best practice would be not to drink and drive.