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Status Report, Vol. 37, No. 7 | August 17, 2002 Subscribe

Risk of phone use while driving isn't easy to pin down

Look around on the roads, and chances are you'll see some drivers gabbing away on cell phones. It's intuitive to most of us that using a phone while driving cannot be a safety plus. Anything that claims the attention of a driver is likely to be hazardous. But a cell phone might not be any more hazardous than other distractions from portable electronics and CD players to route guidance systems. Cell phones might be getting most of the attention these days simply because everyone seems to have a mobile phone. An estimated 137 million people in the United States subscribe to cellular service. That's roughly 3 phone users for every 5 adults.

The answer to whether cell phone use poses a big threat isn't definitive. Much still is unknown about the risks. No one knows how many crashes are related to phone use. Nor is it known whether the collisions tend to be fender-benders or whether they're worse. It's not clear what's most distracting — whether it's primarily holding a phone, dialing it, or conversing on it. There's evidence that all three are risk factors.

So much is unknown because it's inherently difficult to study the effects of driver distraction. A lot has been done on simulators and test tracks, and the results generally suggest that drivers don't perform as well when they're attending to extraneous tasks. But these findings cannot necessarily be generalized to the real world. Getting real-world data that could tie crashes to phone use isn't easy, though there are a few good studies. All of them report that phones are associated with increased crash risk. One 1997 study published in the New England Journal of Medicine analyzed phone billing records for a sample of Canadian drivers in collisions, finding crash risk 4 times higher when drivers were phoning than when phones weren't in use (see "Cell phone use may raise collision risk," March 22, 1997). Other studies report smaller phone-related increases in crash risk, but the findings are limited.

"We need more carefully designed studies using cell phone company records, but the U.S. phone companies seem unwilling to participate," says Allan Williams, the Institute's chief scientist. "We also need to compare the extent of phone use among drivers who don't get in crashes and those who do. Too often you hear that if only the police collected more data on cell phones in their crash investigations, we'd know how big a problem this is. But police reports alone won't provide the answer because they only give information on drivers who crash, not on any comparison group."

Crash scene

The driver of this SUV was talking on the phone when she lost control, crossed a median, and landed on top of a passenger van with four occupants. All five people were killed. Was phoning while driving the main cause of the crash, which occurred last February on a high-speed road in suburban Washington, D.C.? An investigation is under way by the National Transportation Safety Board, which says phone use probably was a factor along with strong winds, vehicle speed, and the driver's inexperience handling the SUV. The safety board expects to issue a report by the end of the year on the contributions of phones and other driver distractions to motor vehicle crashes.

Driver cellphone use drops with N.Y. law

The percentage of drivers using handheld phones dropped by more than half after New York passed a law against it.

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