With the holidays upon us, more drivers than normal are out on the road. It’s the perfect time to remind anyone who’ll get behind the wheel that talking on their cell phones while driving puts their lives, and the lives of others, at risk.

New research backs up the long-held claim, and shows that drivers make more mistakes chatting away on cell phones than when talking to a passenger in the seat next to them.

In the December issue of the Journal of Experimental Psychology: Applied, published by the American Psychological Association, a study finds drivers on cell phones are more likely to drift from their lane, miss their exit, and make other dangerous mistakes.

Drivers using a hands-free cell phone also found their performance at the wheel was significantly compromised. "Cell phone and passenger conversation differ in their impact on a driver’s performance; these differences are apparent at the operational, tactical, and strategic levels of performance," the researchers wrote.

Image above caption: University of Utah psychology graduate students Russ Costa and Janelle Seegmiller demonstrate the driver and passenger roles used by participants in a study of how drivers are affected by conversations with passengers versus conversations over a cell phone. The study, which used the sophisticated driving simulator shown in the photo, found that when drivers talk on cell phones, they are more likely to drift out of their lane and miss exits.
Photo Credit: Nate Medeiros-Ward

Frank Drews, PhD, of the University of Utah, led the study which analyzed the driving performance of 41 mostly young adult drivers paired with 41 friends who served as conversation partners. Both sexes were equally represented.

The study used three experimental conditions (conversation with hands-free cell phone, conversation in the car, or no conversation). One person in each pair was randomly selected to be the "driver" and the other the conversation partner.

A sophisticated simulator that presented a 24-mile multilane highway with on- and off-ramps, overpasses and two-lane traffic in each direction put the drivers to the 10-minute test. They drove under an irregular-flow condition that mimics real highway conditions — with other vehicles, in compliance with traffic laws, changing lanes and speeds. This context required "drivers" to pay attention to surrounding traffic.

In the cell-phone conversation test, conversation partners were at another location. In the in-car conversation option, partners sat next to drivers. All drivers were told to exit the simulated highway once they arrived at a rest area about eight miles from the starting point.

Drivers talking on cell phones drove significantly worse than drivers talking to passengers. The cell-phone users drifted more in their lane, kept a greater distance between their car and the car in front of them, and were four times more likely to miss the instructed rest area exit. Passenger conversation insignificantly affected all three testing options.