ARLINGTON, Va. — Common sense as well as experience tell us that handling and dialing cell phones while driving compromise safety, and evidence is accumulating that phone conversations also increase crash risk. New Institute research quantifies the added risk — drivers using phones are four times as likely to get into crashes serious enough to injure themselves. The increased risk was estimated by comparing phone use within 10 minutes before an actual crash occurred with use by the same driver during the prior week. Subjects were drivers treated in hospital emergency rooms for injuries suffered in crashes from April 2002 to July 2004.
The study, "Role of mobile phones in motor vehicle crashes resulting in hospital attendance" by S. McEvoy et al. is published in the British Medical Journal, available at bmj.com.
"The main finding of a fourfold increase in injury crash risk was consistent across groups of drivers," says Anne McCartt, Institute vice president for research and an author of the study. "Male and female drivers experienced about the same increase in risk from using a phone. So did drivers older and younger than 30 and drivers using hand-held and hands-free phones."
Weather wasn't a factor in the crashes, almost 75 percent of which occurred in clear conditions. Eighty-nine percent of the crashes involved other vehicles. More than half of the injured drivers reported that their crashes occurred within 10 minutes of the start of the trip.
The study was conducted in the Western Australian city of Perth. The Institute first tried to conduct this research in the United States, but U.S. phone companies were unwilling to make customers' billing records available, even with permission from the drivers. Phone records could be obtained in Australia, and the researchers got a high rate of cooperation among drivers who had been in crashes.
Another reason for conducting the study in Australia was to estimate crash risk in a jurisdiction where hand-held phone use is banned. It has been illegal while driving in Western Australia since July 2001. Still one-third of the drivers said their calls had been placed on hand-held phones.
Hands-free versus hand-held
The results suggest that banning hand-held phone use won't necessarily enhance safety if drivers simply switch to hands-free phones. Injury crash risk didn't differ from one type of reported phone use to the other.
"This isn't intuitive. You'd think using a hands-free phone would be less distracting, so it wouldn't increase crash risk as much as using a hand-held phone. But we found that either phone type increased the risk," McCartt says. "This could be because the so-called hands-free phones that are in common use today aren't really hands-free. We didn't have sufficient data to compare the different types of hands-free phones, such as those that are fully voice activated."
Evidence of risk is mounting
The findings of the Institute study, based on the experience of about 500 drivers, are consistent with 1997 research that showed phone use was associated with a fourfold increase in the risk of a property damage crash. This Canadian study also used cell phone billing records to establish the increase in risk. The Institute's new study is the second to use phone records and the first to estimate whether and how much phone use increases the risk of an injury crash.
Taken together, the two studies confirm that the distractions associated with phone use contribute significantly to crashes. Other studies have been published about cell phone use while driving, but most have been small-scale and have involved simulated or instrumented driving, not the actual experience of drivers on the road. When researchers have tried to assess the effects of phone use on real-world crashes, they usually have relied on police reports for information. But such reports aren't reliable because, without witnesses, police cannot determine whether a crash-involved driver was using a phone.