The majority of motorists who talk on a hands-free mobile phone cannot drive without impairment, recent research has found.
As many as 97.5% of those polled by the University of Utah were unable to drive and speak on a hands-free set without the action interfering with their motoring skills.
Just 2.5% of the participants - a minority called 'supertaskers' - were able to talk on their mobile phone while using a driving simulator without noticeable impairment.
When using hands-free mobiles, drivers took 20% longer than required to push the brakes and failed to keep up with simulated traffic, with following distances increasing by 30%.
Their memory performance dropped 11% and the ability to do mathematical problems reduced by 3%.
Co-conductor of the study Jason Watson said: "Given the number of individuals who routinely talk on the phone while driving, one would have hoped that there would be a greater percentage of supertaskers.
"In fact, the odds of being a supertasker are about as good as your chances of flipping a coin and getting five heads in a row."
Ellen Booth, campaigns officer for Brake, said: "It's time that our politicians took note and put an end to the ridiculous situation where using a hand-held mobile is banned, but using hands-free isn't."
© Press Association 2010