|Feb. 1, 2005 -- If
you have been stuck in traffic behind a motorist yakking on a cellular
phone, a new University of Utah study will sound familiar: When
young motorists talk on cell phones, they drive like elderly people,
moving and reacting more slowly and increasing their risk of accidents.
“If you put a 20-year-old driver behind the wheel with a cell
phone, their reaction times are the same as a 70-year-old driver
who is not using a cell phone. It’s like instantly aging a
large number of drivers,” says David Strayer, a University
of Utah psychology professor and principal author of the study.
Frank Drews, as assistant professor of psychology and study co-author,
adds: “If you want to act old really fast, then talk on a
cell phone while driving.”
The new study by Strayer and Drews was published in this winter’s
issue of Human Factors, the quarterly journal of the Human
Factors and Ergonomics Society.
The study found that when 18- to 25-year-olds were placed in a driving
simulator and talked on a cellular phone, they reacted to brake
lights from a car in front of them as slowly as 65- to 74-year-olds
who were not using a cell phone.
The elderly drivers, meanwhile, became even slower to react to brake
lights when they spoke on a cell phone. But the good news for elderly
drivers was that their driving skills did not become as bad as had
been predicted by earlier research showing that older people performing
multiple tasks suffer additional impairment due to aging.
The study found that drivers who talked on cell phones – regardless
of whether they were young or old – were 18 percent slower
in hitting their brakes than drivers who didn’t use cell phones.
The drivers chatting on cell phones also had a 12 percent greater
following distance – an effort to compensate for paying less
attention to road conditions – and took 17 percent longer
to regain the speed they lost when they braked.
In addition, “there was also a twofold increase in the number
of [simulated] rear-end collisions when drivers were conversing
on cell phones,” the study says.
Driving to Distraction: How the New Study was Performed
Strayer and his colleagues are widely known for their 2001 study
showing that hands-free cell phones are just as distracting as
hand-held cell phones, and for a 2003 study showing that the reason
is “inattention blindness,” in which motorists can
look directly at road conditions but not really see them because
they are distracted by a cell phone conversation. The research
has called into question legislative efforts by various states
to ban motorists from using handheld but not hands-free cell phones.
The same researchers also gained publicity for another study,
which was presented at a scientific meeting in 2003, showing that
motorists who talk on cell phones are more impaired than drunken
drivers with blood alcohol levels exceeding 0.08.
The new study included 20 older adults (ages 65 to 74, with average
age 70) and 20 younger adults (ages 18 to 25, with average age
20). All of them had normal vision and a valid driver’s
license. Preliminary tests showed older people were slower to
process information, as was expected.
Then the psychologists had the young and older study participants
“drive” in a high-tech driving simulator. Participants
in the simulator used dashboard instruments, steering wheel and
brake and gas pedals from a Ford Crown Victoria sedan, surrounded
by three screens showing freeway scenes and traffic, including
a “pace car” that intermittently hit its brakes 32
times as it appeared to drive in front of study participants.
If a participant failed to hit their own brakes, they eventually
would rear-end the pace car.
Each participant drove four simulated 10-mile freeway trips lasting
about 10 minutes each, talking on a cell phone with a research
assistant during half the trips and driving without talking the
other half. Only hands-free phones were used to eliminate any
possible distraction from manipulating a hand-held cell phone.
Thirty times each second, the simulator measured the participants’
driving speed, following distance and – if applicable –
how long it took them to hit the brakes and how long it took them
to regain speed. Those factors “have been shown to affect
the likelihood and severity of rear-end collisions,” Strayer
and Drews wrote.
The Findings: Age and Cell Phone Use Impair Drivers
The study found that:
-- Compared with young drivers, older drivers were slower to hit
the brakes when needed, tended to hit the brakes twice, took longer
to regain speed and had a greater following distance. This was
true when young and old participants drove with or without cell
-- Compared with drivers who did not talk on cell phones, those
who used a cell phone while driving were slower to hit the brakes,
had a longer following distance and took longer to regain speed
. This was true of both young and old drivers. “Once drivers
on cell phones hit the brakes, it takes them longer to get back
into the normal flow of traffic,” Strayer says. “The
net result is they are impeding the overall flow of traffic.”
-- When young drivers used cell phones, the reaction time in hitting
the brakes slowed to match that of elderly drivers who did not
talk on cell phones, namely, an average of 912 milliseconds, or
a bit more than nine-tenths of a second. When not talking on cell
phones, young motorists hit the brakes within an average of 780
milliseconds, or almost eight-tenths of a second. The difference
may seem small, but represents a 17 percent slower reaction time.
Strayer says other studies have shown that much of a decrease
in reaction time increases both the likelihood and severity of
-- When elderly drivers used cell phones, their reaction times
got worse, but not as bad as had been expected. Previous research
“suggested older people should have been really messed up
if you put them on a cell phone because, not only are they slower
overall due to age, but there’s a difficulty dividing attention
that should make using a cell phone much more difficult for them
than for young people,” Strayer said. Yet the study “suggests
older adults do not suffer a significantly greater penalty for
talking on a cell phone while driving than do their younger counterparts,”
Strayer and Drews wrote.
That may be because older adults have more experience driving
and take fewer risks, and those in the study may have been healthier
than other seniors, Strayer says.
Crashing While Talking
Federal statistics show that the most accident-prone drivers are
the young and old, with fatal accident rates high during teenage
years, then declining until age 30 and staying relatively level
until age 60, when accident rates climb again as age increases.
Six participants in the new study rear-ended the pace car while
driving the simulator. Four accidents (one older adult and three
younger adults) happened while the participants talked on cell
phones. Two did not (one older adult and one younger adult).
There were too few collisions for statistical analysis. But Strayer
notes that twice as many accidents happened to motorists on cell
phones compared with motorists who were not talking. And young
drivers were in collisions twice as often as elderly drivers.
“Older drivers were slightly less likely to get into accidents
than younger drivers,” Strayer says. “Why? They tend
to have a greater following distance. Their reactions are impaired,
but they are driving so cautiously they were less likely to smash
into somebody,” although in real life, “older drivers
are significantly more likely to be rear-ended” because
of their slow speed.
When Strayer and Drews combined the new accident data with simulated
driving accidents in their earlier studies, they counted 12 rear-end
collisions among 121 study participants. Ten of the collisions
happened when motorists were talking on cell phones.
That is statistically significant and provides “clear evidence
that drivers using a cell phone were more likely to be involved
in a collision than when these same drivers were not using a cell
phone,” the psychologists wrote.