Mobile phone calls, including calls made on hands-free devices, are more distracting to drivers than chatting passengers, according to a study released Monday by University of Utah researchers.
The study, which analyzed the driving performance of 41 adults and their 41 passenger friends, was the latest in a University of Utah series of cell phone use by drivers and was directed by Frank Drews, a Ph.D. researcher at the university.
The researchers set up three separate scenarios: one for conversations with hands-free cell phones, another with in-car conversations between drivers and passengers, and a final scenario with no conversation. A simulator presenting a 24-mile multilane highway complete with on- and off-ramps, overpasses, and two-lane traffic was utilized in the research.
Real highway conditions were mimicked and drivers were told to observe surrounding traffic in each of the three scenarios.
"All drivers were instructed to leave the simulated highway once they arrived at a rest area about eight miles from the starting point," the report said. "The driving sequences took about 10 minutes to finish."
Drivers talking on cell phones tended to drift in their lanes, kept greater distance between their cars and the cars they were following, and were four times more likely to miss pulling off the highway at a prearranged location. Passenger conversations had little effect on the drivers.
So, why did drivers with talkative passengers appear to be safer?
One reason suggested by the researchers was that chatting passengers may actually support drivers by talking about surrounding traffic in a way that helps driver awareness.
