It's the driver. People who talk on cell phones tend to be more unsafe drivers, says a new study from MIT that included a test drive.

Nathan Fried-Lipski/MIT AgeLab

Why Cell Phone Bans Don't Work

You can take the driver away from the cell phone, but you can't take the risky behavior away from the driver. That's the conclusion of a new study, which finds that people who talk on their phones while driving may already be unsafe drivers who are nearly as prone to crash with or without the device. The findings may explain why laws banning cell phone use in motor vehicles have had little impact on accident rates.

The study involved 108 people, equally divided into three age groups: 20s, 40s, and 60s. For each person, the researchers correlated answers on a questionnaire with data collected from on-board sensors during a 40-minute test drive up Interstate 93 north of Boston. The drivers commanded a black Volvo SUV tricked out with an eye tracker, heart and skin monitors, video cameras facing out the front and back windows, on-board sensors, and other research gear.

No cell phones were allowed during these trips. Instead, before they got behind the wheel, the study participants filled in answers about how often they used a cell phone while driving, how they felt about speeding and passing other cars, and how many times in the last year they had been warned or cited for speeding, running traffic lights and stop signs, and other infractions. The team grouped the participants into "frequent users" (those who talked on the phone while driving a few times a week or more) and "rare users" (those who talked while driving a few times a month or less).

Compared with people who rarely talked as they steered, frequent cell phone users drove faster, changed lanes more frequently, spent more time in the left lane, and engaged in more hard braking maneuvers and rapid accelerations, according to the SUV's onboard equipment. Frequent cell phone users, for example, zoomed along about 4.4 kilometers per hour faster on average and changed lanes twice as often, compared with rare users.

"These are not 'oh-my-god' differences," says study leader Bryan Reimer, a human factors engineer at the Massachusetts Institute of Technology (MIT) in Cambridge. "They are subtle clues indicative of more aggressive driving." What's more, he says, other studies have linked these behaviors to an increased rate of crashes. "It's clear [from the scientific literature] that cell phones in and of themselves impair the ability to manage the demands of driving," Reimer says. But "the fundamental problem may be the behavior of the individuals willing to pick up the technology."

The findings, reported online this month in Accident Analysis & Prevention, provide one plausible explanation for why injuries and fatalities from motor vehicle crashes have decreased to historic lows even as cellular technology use has increased dramatically. They may also explain another mystery. "Cell phone bans have reduced cell phone use by drivers, but the perplexing thing is that they haven't reduced crashes," says Russ Rader, a spokesperson for the Insurance Institute for Highway Safety in Arlington, Virginia, who was not involved in the new study. In two other studies, the institute has found no reduction in crashes due to hand-held cell phone or texting bans, based on insurance claim rates in states with and without the laws.

The findings may help explain why legislation banning mobile phone use has had little measurable impact on overall crash rates, speculate the study authors. "There is no question in anyone's mind that talking on a cell phone increases risk," Reimer says. "It's great we can take the phone out of their hands, but these may be the drivers who are getting in accidents anyway."

"We have seen the same correlations in our Traffic Safety Culture Index," says Peter Kissinger, president and CEO of the AAA Foundation for Traffic Safety, an independently funded charitable research and education organization established by the American Automobile Association. The index surveys more than 3100 people each year. The foundation wants to change driver behavior, a challenge more complex than banning phones, he says.

Still, cell phone bans may save lives, says David Strayer, a cognitive neuroscientist at the University of Utah in Salt Lake City. "The MIT data indicate that regulation [banning cell phone use] may be reasonable so long as it is followed up with good enforcement, and that together these would result in a decrease in unsafe driving behavior."