The University of Utah's Traffic Lab found that drivers who use cell phones behind the wheel impede the flow of traffic and extend commute times.
Prior studies have equated the risk of driving while talking on a cell phone with driving while drunk. Some 50 countries have banned use of hand-held phones while driving.
The study showed tha when drivers were distracted by a phone conversation, they made fewer lane changes, drove slower and took longer to get where they are going. It made no difference if they used a hands-free phone.