More drivers than ever are talking on cell phones. The National Highway Traffic Safety Administration (NHTSA) reports that at any time of day 6 percent of drivers on U.S. roads in 2005 were using hand-held phones — double the rate that was observed 5 years ago. The highest phone use rate in 2005 (10 percent) was among drivers 16 to 24 years old.
"It's troubling that the youngest drivers are the most likely to be talking on phones," says Anne McCartt, Institute research vice president. "These drivers already have higher crash rates than older drivers, including higher fatal crash rates, and the last thing they need is the distraction of using a phone."
NHTSA's report on hand-held phone use is based on observational studies. Based on these plus telephone interviews, NHTSA also has estimated the use of hands-free phones and other electronics while driving. The agency says as many as 10 percent of motorists of all ages may be using some type of phone, either hand-held or hands-free.
Lots of study approaches, one message
The NHTSA survey results were released last month, the same time as a new Institute review of available evidence about the safety consequences of phoning while driving. McCartt and other Institute researchers reviewed 125 studies in all.
Almost half of the cell phone studies were experimental, involving tests of small numbers of people in driver simulators or instrumented vehicles. Almost all of these studies identified effects on driver performance from the cognitive distractions associated with phone use. For example, the reaction times of drivers using phones were likely to be slower. Drivers on phones also were more likely to deviate from their lanes. However, many of these studies didn't involve driving or phoning tasks that were realistic, so it's hard to draw meaningful conclusions about the risks for real motorists in everyday driving situations.
A handful of studies did involve real drivers on the road with cameras or other technologies in their vehicles to record their behavior. One of these so-called naturalistic studies found that drivers were more likely to take their hands off the steering wheel or their eyes off the road when they were dialing a phone or answering it.
Most studies of real-world crashes have used data obtained from crash-involved drivers or reports by police who queried the drivers about whether a cell phone was being used at the time of a crash. These aren't reliable sources of information. A few studies have used cell phone companies' billing records — much more reliable information sources — to verify phone use by drivers who were in crashes. An Institute study based on the billing records of Australian drivers found a fourfold increase in the risk of an injury crash associated with phone use. This risk was consistent among male and female drivers as well as younger and older drivers (see "Using a phone while driving raises the risk of a crash with injuries," July 16, 2005). A Canadian study found about the same increase in the risk of a property damage crash.
These two studies of real-world crashes also found about the same risk associated with hands-free and hand-held phones. This is consistent with experimental studies showing that driver performance is affected by hands-free and hand-held phone use alike.
"Such findings have implications for the kinds of laws being enacted or being considered by state legislators to reduce the risks of phone use," McCartt says.
Laws restricting cell phone use
A number of jurisdictions worldwide, including several U.S. states, make it illegal to use a hand-held phone while driving. Such bans are in effect in Connecticut, New Jersey, New York, and the District of Columbia. Ten states and D.C. limit the use of any kind of phone by teenage drivers, and in 11 states and D.C. the limit applies to school bus drivers. The effects of the bans have varied.
An initial decline in hand-held phone use right after New York enacted its 2001 law didn't persist (see "Hand-held cell phone use goes back up in N.Y., despite year-old ban," Aug. 26, 2003). It dissipated within about 18 months. However, a new study of D.C.'s law indicates a more lasting result. This jurisdiction began banning handheld phone use while driving in July 2004. The use rate declined from about 6 percent before the law to 3.5 percent 3 months after it took effect. A year later, this decline was being sustained. Hand-held phone use did go up a little bit but not much — and relative to the substantial increases in phone use in nearby jurisdictions the D.C. use rate still was 50 percent lower than before the law took effect.
"It's unclear why the laws in these two jurisdictions haven't had similar influences on drivers, but it might have something to do with D.C.'s reputation for strong enforcement of traffic laws," McCartt says. Citations for cell phone violations represented 8 percent of all moving violations in D.C. compared with 4 percent in New York.
Enacting and enforcing laws like D.C.'s in every state might convince many drivers to abandon their hand-held phones. But if these drivers were to simply switch to hands-free phones, the effects might not be as beneficial as lawmakers expect. After all, the studies conducted in Australia and Canada found approximately equal increases in the risk of a crash regardless of the type of phone a driver was using.
No jurisdiction prohibits all drivers from using hands-free phones. Why not? A problem is that such a law would be difficult to enforce. It would be hard for police to see if a driver were talking on a hands-free phone.
"Increasing the number of states that ban hand-held phone use might be beneficial to the extent that not all drivers would make the switch to hands-free. Some of them would stop using their phones altogether while they're behind the wheel, which would reduce the risk of crashing," McCartt concludes.
Percentage of drivers talking on hand-held phones, 2000-05
Source: National Occupant Protection Use Survey, National Center for Statistics and Analysis, National Highway Traffic Safety Administration