Evidence of Effects of Cell Phone Use on Injury Crashes: Crash Risk is Four Times Higher When Driver is Using Hand-Held Cell Phone

Text courtesy of Insurance Institute for Highway Safety

More:  Visitor Feedback (Below)

Common sense as well as experience tell us that handling and dialing cell phones while driving compromise safety, and evidence is accumulating that phone conversations also increase crash risk. 

New Institute research quantifies the added risk — drivers using phones are four times as likely to get into crashes serious enough to injure themselves.  The increased risk was estimated by comparing phone use within 10 minutes before an actual crash occurred with use by the same driver during the prior week.  Subjects were drivers treated in hospital emergency rooms for injuries suffered in crashes from April 2002 to July 2004.

The study, "Role of cellular phones in motor vehicle crashes resulting in hospital attendance" by S. McEvoy et al. is published in the British Medical Journal.

"The main finding of a fourfold increase in injury crash risk was consistent across groups of drivers," says Anne McCartt, Institute vice president for research and an author of the study.  "Male and female drivers experienced about the same increase in risk from using a phone.  So did drivers older and younger than 30 and drivers using hand-held and hands-free phones."

Weather wasn't a factor in the crashes, almost 75 percent of which occurred in clear conditions.  Eighty-nine percent of the crashes involved other vehicles.  More than half of the injured drivers reported that their crashes occurred within 10 minutes of the start of the trip.

The study was conducted in the Western Australian city of Perth.  The Institute first tried to conduct this research in the United States, but U.S. phone companies were unwilling to make customers' billing records available, even with permission from the drivers.  Phone records could be obtained in Australia, and the researchers got a high rate of cooperation among drivers who had been in crashes.

Another reason for conducting the study in Australia was to estimate crash risk in a jurisdiction where hand-held phone use is banned.  It has been illegal while driving in Western Australia since July 2001.  Still one-third of the drivers said their calls had been placed on hand-held phones.

Hands-free versus hand-held: The results suggest that banning hand-held phone use won't necessarily enhance safety if drivers simply switch to hands-free phones. Injury crash risk didn't differ from one type of reported phone use to the other.

"This isn't intuitive.  You'd think using a hands-free phone would be less distracting, so it wouldn't increase crash risk as much as using a hand-held phone.  But we found that either phone type increased the risk," McCartt says.  "This could be because the so-called hands-free phones that are in common use today aren't really hands-free.  We didn't have sufficient data to compare the different types of hands-free phones, such as those that are fully voice activated."

Evidence of risk is mounting: The findings of the Institute study, based on the experience of about 500 drivers, are consistent with 1997 research that showed phone use was associated with a fourfold increase in the risk of a property damage crash.  This Canadian study also used cell phone billing records to establish the increase in risk.  The Institute's new study is the second to use phone records and the first to estimate whether and how much phone use increases the risk of an injury crash.

Taken together, the two studies confirm that the distractions associated with phone use contribute significantly to crashes.  Other studies have been published about cell phone use while driving, but most have been small-scale and have involved simulated or instrumented driving, not the actual experience of drivers on the road.

When researchers have tried to assess the effects of phone use on real-world crashes, they usually have relied on police reports for information.  But such reports aren't reliable because, without witnesses, police cannot determine whether a crash-involved driver was using a phone.

 Visitor Feedback

From "M-A-D-D Ray" Henke:  "(Your) article is useful but it doesn't go far enough. First of all, it reports only one of the epidemiological studies, and in that somewhat dated study the authors are reported as unsure about what accounted for the lack of difference between the use of handheld and hands-free cellphones in their results, offering speculation which has subsequently been determined to be inaccurate.

The epidemiological work was supplemented by the controlled experimental work of Strayer et al. and the neurological work of Yantis at Johns Hopkins.  These studies have not only confirmed the DUI level impairment and 4 fold increased likelihood that the cell phone impaired will cause an accident, they also explain why those who use handheld cell phones and those who use hands-free cell phones are equally impaired. In a few words, the impairment results from the conversation itself, not from holding or manipulating the cell phone.  It results from the shifting of attention to the internal cognitive tasks associated with the give and take of the cell conversation away from the external visual tasks essential for safe driving.

Your article was posted on Bruce-n-Ray's Biker Forum, a site that I co-moderate, and I will reprint my supplementary memorandum below.  But I have written a much more comprehensive article on the subject, which appears (here) and cites to the all of the epidemiological literature, the controlled experimental studies and the converging neurological work.

If you would like to reprint that article to supplement yours with the more complete and up to date scientific information, you have my permission.  I would just request that you give credit as contained in the article, to Motorcyclists Against Dumb Drivers and provide the link to the page or to the main page of the web site, as there are also follow up articles on the subject of interest to motorcyclists wanted to look at the articles additional implications.

One, for example, is to provide additional evidence to counter NHTSA's pitch based on population studies that the increased incidence in motorcycle deaths is the result of hypothetical characteristics of biker behavior, e.g., helmet use, shift to riding by older bikers, etc.  There is also a wonderful article by a thoughtful libertarian explaining why he has come to the conclusion that he favors both helmet bans and strong prosecution of those who cause accidents as the result of their use of cell phones while driving...

...Thank you for your consideration.  I feel that this is a very important issue for bikers particularly because like pedestrians and bicyclists, we are much more vulnerable to the accidents which the cell phone impaired cause.

Article:  The Epidemiological Studies Referred to Have Been Supplemented by the Controlled Experimental Studies and Neurological Studies, Making Plain Both That The DUI Impairment is the Same for Handheld and Hands-Free Cell Phones, and Why the Impairment is the Same.

The British Medical Journal article referred to in the above article was important because it "replicated" the findings of the original epidemiological work published New England Journal of Medicine.  The epidemiological work is important because it is a real world demonstration that drivers on the street who engage in cell conversation while driving suffer an impairment equivalent to driving DUI under the influence of alcohol, and the four fold increased likelihood that the driver would cause an accident.

As noted, the British Medical Journal study did not find a difference between handheld and hands-free cell phone use and the impairment or increased incidence of accidents.

In the above article the authors speculate as to the reason why there was no difference found between handheld and hands-free cell phone use.  But there is no reason any longer for speculation, as the answers have been provided by the controlled experimental studies. The controlled experimental studies have found that reason is because the impairment doesn't stem from holding or fiddling around the phone, it is an in-attentional blindness resulting from the cell conversation itself.

It is an in-attentional blindness resulting from the shifting of limited conscious attention to the internal cognitive tasks associated with the give and take of the cell conversation away from the external visual tasks associated with safe driving.  When you are engaged in driving while on the cell phone you intermittently actually don't "see" what is right in front of you.  The controlled experimental studies found that drivers using handheld and hands-free cell phones will not "see" even what their eyes are fixed upon, and they won't "see" significant changes in the driving environment that would normally automatically attract attention.

These epidemiological studies, followed by the controlled experimental studies were then complimented by the recent neurological studies in MRI studies tracked the brain activity of the subjects while on the cell phone and found that activity in the brain shifted back and forth between the visual center and the auditory center, with a third center identified as one which was involved in the switching process.  The author of that Johns Hopkins study specifically described the result as an in-attatentional blindness and suggested that his work explains why handheld and hands-free cell phones would have the same effect.

It is all this evidence, the epidemiological work, the controlled experimental work and then the converging neurological work which makes it scientifically plain both that cell phone use while driving results in DUI level impairment, and that the impairment is the same whether the driver uses a handheld or hands-free cell phone.