A study has shown that driving while using a mobile phone is as bad as driving with a blood-alcohol level over the limit.

Researchers at the University of Utah put 40 volunteers into a driving simulation device to compare their driving under four separate situations.

The drivers were checked while undistracted, while using a handheld mobile, while using a hands-free mobile, and while at 0.08% blood-alcohol level.

Three of the volunteers drove into the back of the car in front while talking on mobiles, and those who talked tended to drive more slowly and also to react more slowly.

When at a 0.08% blood alcohol level, drivers were slower but more aggressive.

Professor Drews, one of the researchers at the university, said, "Driving while talking on a cellphone is as bad as or maybe worse than driving drunk".