Drivers spend 18% of their time behind the wheel not watching the road at all, according to sophisticated research by insurer Direct Line.

Instead motorists apparently gaze at clouds, scenery, adverts and other non-driving related distractions, on average taking their eyes off the road every nine seconds.

The investigation utilised advanced eye-tracking technology to record drivers' eye movements, finding that motorists using sat-nav devices were distracted even more frequently, with 22% of their journey spent focusing away from the road.

Participants were asked to wear specialist glasses that pinpoint the exact focus of the eye by tracking microscopic movements in the cornea. The results were then mapped onto video footage also taken by the glasses, enabling researchers to establish exactly where drivers focus their vision.

Among the key statistics are that sat-nav users spend on average 12% of their journey time looking at the navigation screen. Direct Line surmises that during a 90-minute journey from London to Brighton a sat-nav user will spend a total of 11 minutes looking solely at the device.

The figures also mean that drivers with navigation equipment spend six times longer looking at its readout than they do at oncoming traffic.

Drivers spend 7% of their time behind the wheel looking at clouds and scenery, 3.2% of the trip checking their mirrors and 2% watching oncoming traffic. The research also found that people spend 0.8% of the time looking at adverts.

Interestingly, while men and women were both seen to be distracted by `attractive pedestrians', with 3% of their driving time spent ogling, only men turned their heads fully away from the road to look.

Simon Henrick, spokesperson for Direct Line car insurance said, "For the first time we know exactly where people focus their eyes when driving and the results are frightening.

"Even when drivers appear to be watching the road, by tracking movements in the cornea we now know they are often watching clouds or shop window displays. It is important that every time a driver gets behind the wheel that they concentrate for the whole journey, otherwise they risk injuring themselves and others."