Cell phone crash risk overestimated

Conveniently timed to coincide with the NTSB recommendation to ban cell phone use while driving.

From a Wayne State University media release:

Wayne State study shows early research on cellphone conversations likely overestimated crash risk

DETROIT — A Wayne State University study published in the January 2012 issue of the journal Epidemiology points out that two influential early studies of cellphone use and crash risk may have overestimated the relative risk of conversation on cellphones while driving.

In this new study, Richard Young, Ph.D., professor of research in Wayne State University’s Department of Psychiatry and Behavioral Neurosciences in the School of Medicine, examined possible bias in a 1997 Canadian study and a 2005 Australian study. These earlier studies used cellphone billing records of people who had been in a crash and compared their cellphone use just before the crash to the same time period the day (or week) before — the control window.

Young said the issue with these studies is that people may not have been driving during the entire control window period, as assumed by the earlier study investigators.

“Earlier case-crossover studies likely overestimated the relative risk for cellphone conversations while driving by implicitly assuming that driving during a control window was full time when it may have been only part time,” said Young. “This false assumption makes it seem like cellphone conversation is a bigger crash risk than it really is.”

In Young’s new study, his research team used Global Positioning Satellite (GPS) data to track day-to-day driving of more than 400 drivers during a 100-day period. He then divided the days into pairs, with the first day representing the “control” day and the second day representing the “crash” day in the earlier studies. Overall, the team found little driving consistency in any given clock time period between the two days — driving time on the control day was only about one-fourth of the driving time on the crash day, during any specific clock time period.

“This underestimation of the amount of driving in the control windows by nearly four times could reduce cellphone conversation time in that control period,” Young said. “It makes it appear that there is less cellphone conversation in control periods than in the time just before a crash, making the relative risk estimate appear greater than it really is.”

Young found that when the cellphone conversation time in the control window was adjusted for the amount of driving, the amount of cellphone usage in the control window was about the same as in the minutes before a crash. He concluded that the crash risk for cellphone conversation while driving is one-fourth of what was claimed in previous studies, or near that of normal baseline driving.

Young added that many well-controlled studies with real driving show that the primary increase in crash risk from portable electronic devices comes from tasks that require drivers to look at the device or operate it with their hands, such as texting while driving. Five other recent real-world studies concur with his conclusion that the crash risk from cellular conversations is not greater than that of driving with no conversation.

“Tasks that take a driver’s eyes off the road or hands off the steering wheel are what increase crash risk,” said Young. “Texting, emailing, manual dialing and so forth — not conversation — are what increase the risk of crashes while driving.”

The National Transportation Safety Board has recommended that all 50 states and the District of Columbia ban the non-emergency use of portable electronic devices for all drivers. Young said this recommendation goes beyond the data from newer studies, including his, because it would ban cellphone conversations while driving.

“Recent real-world studies show that cellphone conversations do not increase crash risk beyond that of normal driving — it is the visual-manual tasks that take the eyes off the road and the hands off the wheel that are the real risk,” said Young.

Click for “NTSB recommends full ban on use of cell phones while driving”.

4 thoughts on “Cell phone crash risk overestimated”

  1. The near misses on your bike very likely were on purpose. Most drivers hate bicyclists and like to make it tough on you guys.

    Have you ever considered that while you are exercising by bicycling, you put yourself in a higher category for bodily injury?

    I cannot count on all my fingers and toes how many of my cyclist friends who get seriously injured while road cycling (dodging cars, dogs, etc.) and mountain biking.

    They prefer the winding roads of East Tennessee instead of the wide open U.S. Highways. Go figure.

  2. David, the general reasoning is that distracted, bad drivers talk irresponsibly on cell phones. If they have no cell phone, they are being careless and irresponsible by doing something else. Responsible drivers talk responsibly on the cell phone. I talk on the phone without incident every day (over an hour commute, I have to do something with my time). However, if traffic is heavy, I hang up because the road has to command my full attention.

    Several studies have shown that there is no affect on crash rates when a cell phone ban is passed, and Hawaii even bandied about repealing it after a year. It’s like red light cameras. Intuitively, it should help make roads safer, but it doesn’t.

  3. This cell phone warning needs to “show me the bodies!”

    The NHTSA website has the statistics on fatal crashes since 1990. They have fallen 20% since 2006! (2010 was slightly higher with only a 17% reduction)

    I would think 2007 to 2010 would have a large increase in cell phone usage as the iPhone and other smart phones started to come out (2011 is not yet reported), but clearly this did not increase the overall fatality rate. Property damage only crashes are also down. I don’t know what problem cell phones are perceived to cause, but the statistics show things are getting better.

    With data so readily available and with a clear downward trend in crashes, the media should be ashamed to report this sort of junk-science.


  4. Yah, three times last summer I almost got hit on my bicycle in small town Montana by idiots either talking or texting. Put them all in jail. Once in the summer of 2010 in SE Wisconsin I almost got hit head on in my half ton by a girl texting and driving. I jumped lane and pounded the horn and she finally looked up. Yah, it does not matter.

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