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June 29, 2006 -- Driving under the influence of a cell phone may be a major road hazard, according to a University of Utah study.
"The impairments associated with using a cell phone while driving can be as profound as those associated with driving while drunk," write psychology professor David Strayer, PhD, and colleagues in the summer issue of the journal Human Factors.
Strayer's team tested the driving skills -- on a simulator, not real roads -- of 25 men and 15 women under four conditions:
Driving with a blood-alcohol concentration of 0.08% or higher is against the law in all U.S. states and Washington, D.C.
Chatting Behind the Wheel
The simulator resembled a Ford Crown Victoria sedan. Participants were to drive along a simulated stretch of highway without crashing into the car ahead of them, which braked at unpredictable times.
The drivers were 22-34 years old (average age: 25). They had good eyesight, valid drivers' licenses, and an average of eight years of driving experience. More than three-quarters owned a cell phone; almost all of those drivers -- 87% -- said they have used a cell phone while driving.
In the cell phone tests, participants chatted on a cell phone about a favorite topic. They spoke with a research assistant, and they didn't have to dial the phones or answer the phones while driving.
Cell Phone Crashes
While on either type of cell phone (hands-free or hand-held), drivers were more likely to rear-end the car ahead of them than when they were undistracted. They were also slower to brake and to accelerate after braking while on either type of cell phone.
No differences were seen between the use of hands-free or hand-held cell phones while driving. The conversation itself -- not the device -- may be the biggest distraction, note Strayer and colleagues.
"Clearly the safest course of action is not to use a cell phone while driving," the researchers write. They add that when they interviewed participants after the study, most hadn't realized that their driving was worse while on the cell phone.
Driving While Drunk
For the drunk-driving test, participants downed enough vodka and orange juice at the lab to send their blood-alcohol concentration to the legal limit, which was confirmed by a breathalyzer machine.
While drunk, participants drove more aggressively than when they were sober, the study shows. They tailgated the car ahead of them and had to slam on the brakes when the lead car slowed down.
None of the drunk drivers had any "crashes" in the simulated test. That might be because the tests were done in the morning; most drunk-driving accidents happen at night, when fatiguefatigue may also be a factor, the researchers note.
The researchers stress that drunk driving is a major danger and that participants' drunk-driving patterns made accidents likely.
SOURCES: Strayer, D. Human Factors, Summer 2006; vol 48: pp 381-391. Insurance Institute for Highway Safety: "DUI/DWI Laws." News release, University of Utah.