The study found that the subjects involved in phone conversations showed significantly slower responses to traffic signals and missed signals entirely much more often than subjects who were listening to the radio or a book on tape. There was no measurable difference, however, in driver responses among those subjects using hand-held phones and those using hands-free devices.
According to the authors, this indicates that the loss of responsiveness motorists experience while using cell phones is not due solely to holding or dialing a phone. The scientists concluded that it was the active engagement in a conversation that caused the higher levels of driver distraction.
The issue of driver distractions caused by cellular phones becomes increasingly important as cell phone use becomes more prevalent in American life. According to studies conducted by the National Highway Traffic Safety Administration (NHTSA), some form of driver distraction is a contributing factor in 20 to 30 percent of all crashes. The Cellular Telephone Industry Association estimates that there are currently 120.1 million cellular phones in operation in the United States, and a recent NHTSA survey found that nearly 75 percent of drivers reported using their phone while driving. A NHTSA observational study released last month estimated that 500,000 drivers of passenger vehicles (cars, vans, sport utility vehicles and pickups) are talking on hand-held cell phones during any given daytime moment throughout the week.
In a "Multitasking Statement" adopted by the National Safety Council in March of this year, the Council noted that "a driver's first responsibility is the safe operation of the vehicle" and that "best practice is to not use electronic devices including cell phones while driving." The statement can be found on the Council's website.