This is the latest article showing that cell phones impair a driver's ability to concentrate and react ("Cell Phone Use Ages Young Drivers"). Some interesting highlights below...

A report from the University of Utah says when motorists between 18 and 25 talk on cell phones, they drive like elderly people moving and reacting more slowly and increasing their risk of accidents. "If you put a 20-year-old driver behind the wheel with a cell phone, his reaction times are the same as a 70-year-old driver," said David Strayer, a University of Utah psychology professor and principal author of the study. "It's like instant aging." And it doesn't matter whether the phone is hand-held or handsfree, he said. Any activity requiring a driver to "actively be part of a conversation" likely will impair driving abilities, Strayer said.

Motorists who talk on cell phones are more impaired than drunken drivers with blood-alcohol levels exceeding 0.08, according to research conducted in 2003. Strayer said they found that when 18- to-25-year-olds were placed in a driving simulator and talked on a cellular phone, they reacted to brake lights from a car in front of them as slowly as 65- to 74-year-olds who were not using a cell phone. The study found that drivers who talked on cell phones were 18 percent slower in braking and took 17 percent longer to regain the speed they lost when they braked.

The new research questions the effectiveness of cell phone usage laws in states such as New York and New Jersey, which only ban the use of hand-held cell phones while driving. It's not so much the handling of a phone, Strayer said, but the fact that having a conversation is a mental process that can drain concentration.