A new study, led by the University of Utah’s David Strayer and published in the Journal of Experimental Psychology: Applied, finds that using a mobile phone is far more distracting to automobile drivers than even the most talkative of passengers, significantly slowing reaction times and leading drivers to drift out of their lanes, miss exists to such a level that resemble drunk drivers. In fact, having a passenger in the car is actually a good thing, since they act as a "second set of eyes" and help the driver keep and eye on the road and where the car is headed? And hands-free devices? Not as much help as some people might think.
The study involved a series of experiments among 96 adults aged 18 to 49 in a driving simulator, and found that drivers using mobile phone headsets were more likely to miss exit while talking (WMV video), as well as drift out of their lanes. Conversely, drivers talking a passenger were not impaired to the same degree.
Strayer’s previous studies have found that using mobile phones while driving slows response times, bringing the reaction levels of young adult drivers down to those of senior citizens and even drivers who were legally drunk.
Unlike someone on the other end of a mobile phone call, even chatty passengers in a car are prone to simplify or stop their conversations when driving conditions change, enabling a driver to focus more intently on the road and operating the vehicle.