Calls and Motor Vehicle Collisions.
Donald A. Redelmeier, MD, and Robert J. Tibshirani, PhD.
The New England Journal of Medicine, February
13, 1997, 336(7): 453-458.
Study Finds Cellular Telephone Use Contributes
to Motor Vehicle Accidents
Association Between Cellular-Telephone
Calls and Motor Vehicle Collisions.
Donald A. Redelmeier, MD, and Robert J. Tibshirani, PhD.
The New England Journal of Medicine, February
13, 1997, 336(7): 453-458.
In the first significant study of care telephone use and roadway accidents,
researchers Redelmeier and Tibshirani found that drivers using a cellular
telephone were four times more likely to be in a motor vehicle collision
than drivers who didn't. This risk is similar to that of driving under the
influence of alcohol when the blood alcohol level is at the legal limit according
to the researchers.
The researchers studied motor vehicle collisions in Toronto. They compared
the times of cellular-telephone calls, obtained from billing records, with
the times collisions took place. Based on this data, the researchers estimated
that cellular telephone user risk of a collision was between 3.0 and 6.5
times higher within 10 minutes after a telephone call began than the risk
when a cellular telephone was not in use.
Lawmakers in a number of countries are taking a serious look at the risk
of using cellular telephones when driving and regulating their use.
The researchers cautioned against interpreting their results 'as showing
cellular telephones are harmful and that their use should be restricted."
They note their research shows an association but not necessarily a direct
cause relationship between cellular telephone use and collisions. In looking
at the risks, they stress that the benefits of cellular telephone use and
individual responsibility need to be taken into account. They cited in Canada
alone half a million calls are made annually from cellular telephones to
911 emergency services.
The study included 699 drivers who had cellular telephones and were involved
in collisions resulting in extensive property damage but no personal injuries.
In all, 24 percent used their cellular telephone within the 10-minute period
prior to the collision.
The cellular telephone bills for each driver for the day of the collision,
as well as for the week prior to the accident, were reviewed. The researches
used case-crossover analysis to assess the brief change in risk associated
with transient cellular telephone use. With this method, each study subject
served as his or her own control. The researchers compared the conditions
at the time of the accident with conditions during a control period prior
to the accident for each driver. The case-crossover analysis identified an
increase in risk by finding that more cellular telephone calls were made
right before a collision than could be expected solely by chance.
Among other findings of the study:
- The relative risk of collision was similar among subgroups (male/female, type of job, driving experience, cellular telephone use experience) though younger drivers were at a somewhat higher risk.
- The highest relative risk for collision was among those who were not high school graduates.
- The increase in risk for an accident as greatest for calls made within five minutes of the collision.
- The accident risk for calls made more than 15 minutes prior to a collision were not found to be statistically significant.
- Telephones that left hands free did not appear to be safer than hand-held
telephones.
The researchers point out three weaknesses in their study:
1. Only drivers who consented to take part were included. This may have caused them to underestimate the risks of cellular telephone use of people who declined to take part because of concern for personal liability.
2. People's driving behavior can vary from day to day.
3. Case-crossover analysis does not eliminate all imbalances in temporary
conditions related to the driver, vehicle, or environment between the control
period and the time of the accident. However, the authors did not believe
that these factors significantly affected their findings.
The study data did not show who was at fault for the collisions. The
researchers suggest that cellular telephone use may have reduced a user's
ability to avoid an accident that wasn't the user's fault.
While regulating cellular telephone use is controversial, the researchers note that "the role of the individual is clear." Because cellular telephone users are at greater risk for a motor vehicle accident, they should take special precautions including not placing or receiving unnecessary calls, interruption conversations if necessary, and keeping calls brief -- especially under hazardous driving conditions.
