Car phones jack up risk of collisions.

Driving while phoning may soon become as notorious a traffic offense as driving while intoxicated. Both practices at least quadruple a driver's risk of having a collision, a new study shows.

Donald A. Redelmeier and Robert J. Tibshirani of the University of Toronto have produced what may be the first large-scale evidence of car phone risk. They studied 699 Canadian drivers with telephones, all of whom were "involved in motor vehicle collisions resulting in substantial property damage but no personal injury."

The researchers drew their data from the drivers' cellular telephone records, police accident reports, and interviews with the drivers themselves. They then analyzed the drivers' telephone use on the day of their vehicular crack-ups and on the day before the collision.

Redelmeier and Tibshirani chose this method because it would enable them to "identify an increase in risk if there were more telephone calls immediately before the collision than would be expected solely as a result of chance."

The investigators found that each driver used the car phone an average of nine times on days in which collisions occurred. Twenty-four percent of the drivers had begun a call within 10 minutes of the collision. By comparing the same drivers' calling patterns on the previous day, the researchers calculated that phone use increased the likelihood of a collision 4.3 times.

The duo decided against analyzing collisions that involved serious injury, because they did not want personal injury lawyers to seize on the study as potential evidence in lawsuits. In court, the researchers might have to violate their vow of privacy to the people who volunteered for the research, Redelmeier says.

The study, published in the Feb. 13 New England Journal of Medicine, provides "the first direct evidence" that cellular phones contribute to roadway collisions, Malcolm Maclure of the Harvard School of Public Health and Murray A. Mittleman of Beth Israel Deaconess Medical Center, both in Boston, write in an accompanying editorial.

The study does not suggest that people who were using cellular phones caused collisions, Redelmeier emphasized. Many of the drivers couldn't avoid cars that veered into them-even when using phones that allowed them to keep two hands on the steering wheel.

"I thought that the most striking observation was that hands-free cellular telephones offered no large safety advantage, suggesting that the major factor in a motor vehicle collision was not limited manual dexterity, but the driver's limited attention," Redelmeier says. Nearly 40 percent of the drivers used their phones to call for aid after the collision, he added. Half a million Canadians use cell phones to report emergencies each year.

Maclure and Mittleman found that the risk of a collision doubles within 5 minutes of starting a phone call. They calculate that if 1 driver in 10 has a car phone by the year 2000, driving while phoning could cost the United States alone up to $4 billion per year.