Cell phones and driving: what the science says

The New York Times is running a series on the evils of cell phone use while driving. Its latest article is chock-full of anecdotes about serious accidents caused by cell-phone use, and laments how people are not responding to the research:

Extensive research shows the dangers of distracted driving. Studies say that drivers using phones are four times as likely to cause a crash as other drivers, and the likelihood that they will crash is equal to that of someone with a .08 percent blood alcohol level, the point at which drivers are generally considered intoxicated. Research also shows that hands-free devices do not eliminate the risks, and may worsen them by suggesting that the behavior is safe.

A 2003 Harvard study estimated that cellphone distractions caused 2,600 traffic deaths every year, and 330,000 accidents that result in moderate or severe injuries.

Yet Americans have largely ignored that research.

This line of argument has always struck me as asinine. It makes good sense to require drivers to have both hands available, so I’ve never been opposed to hands-free requirements. But opposing cell-phone use because it is distracting misses one major point: there are lots of distractions while we drive. We listen to the radio, we talk to people in the car, we have screaming children. (And those are just the reasonable things; there’s also stupid things like eating or applying make-up.) How do the risks of cell phone usage compare to all those other distractions? It seems likely that using a hands-free cell phone is more distracting than listening to the radio, about the same as talking to someone in the car, and quite a bit less than screaming children. But no one is talking about banning carpools, which surely lead to in-car conversations, or banning the transporting of children.

The NYT article did have something useful though. It had a link to a Department of Transportation publication containing an up-to-date (as of 2005) bibliography of research on the subject. On the assumption that the most respectable research appeared in peer-reviewed journals (this is the case in most fields, although not as much in mine), I looked up a handful of the articles on-line. In three cases I was able to find the actual paper, and in three I had to settle for the abstract.

What I found surprised me. None of the abstracts (nor the full papers when I could find them) discussed comparisons between cell-phone use and other distractions. In this, I imagine I was just unlucky (surely someone has looked at the question). But I did notice that all the studies were more measured that the reporting would suggest.

The most interesting was the 2003 Harvard study to which the NYT article alluded. As an aside, it did estimate that eliminating cell phone use would save 2600 lives. But that is not what the study was about. The study did a cost-benefit analysis. It built an economic model and compared the costs of a cell phone ban against the benefits in terms of lives and property saved.

The study found that eliminating cell phone use would be a break-even proposition. In fact, it would be a small net loss. And that doesn’t take into account the intangible cost of the reduction of our liberty. The study also found that eliminating cell phone are a very expensive way to save lives when compared with other possible safety measures. Finally, it’s worth noting that even a total ban on cell phone usage would not eliminate cell phone usage, nor would it probably even come close (see below).

More after the jump.

Aside from the Harvard study, I looked at both journal articles from 2005, and a selection from 2004 whose titles suggested they were specifically directed toward driving:

  • One study (“Factors influencing the use of cellular (mobile) phone during driving and hazards while using it”) showed that drivers are being responsible (or at least trying) in their use of cell phones, concluding:

    This study clearly indicates that potential risks of mobile phones are being controlled at many levels, by strategic as well as tactical decisions and, consequently, phone-related accidents have not increased in line with the use of the mobile phones.

  • Another study (“Effects of practice, age, and task demands, on interference from a phone task while driving”) showed that drivers who use cell-phones get better at it over time:

    The deleterious effects of conversing on the phone are very real initially, but may not be as severe with continued practice at the dual task, especially for drivers who are not old.

  • Another study showed that drivers use cell-phones less when driving at night or over the speed limit.
  • Yet another study showed that merely listening attentively does not have the same negative effects as a two-way conversation.
  • Finally, one study looked at the effect of banning hand-held cell phones in Connecticut and New York (two of the three states with such bans). The study showed that the bans are widely ignored. In Connecticut it had no discernable effect. In New York, use declined significantly at first, then rose back to nearly the same level.

My conclusion is that the advocates of cell-phone prohibition are not telling the whole story. To be sure, using cell phones can cause dangerous distraction. However, there are a number of factors moderating that effect, and if there is any research showing that cell phones are worse than other distractions, I was unable to find it. Moreover, there are much more cost-effective ways to save lives.

ASIDE: One cost-effective way to save lives that wasn’t mentioned in the Harvard study would be to repeal CAFE standards. Doing so would save half as many lives as banning cell phones would, at a fraction of the cost. (And that’s before President Obama’s big hike in CAFE standards.)

Personally, I try to limit my use of a cell phone while driving. But sometimes it is important and I don’t want that right taken away.

UPDATE (12/15/2011): The DOT publication is 404 now, but you can find it on the Wayback Machine.


One Response to Cell phones and driving: what the science says

  1. […] study estimates that cell phone use behind the wheel causes 2,600 traffic fatalities a year, The New York Times reports. Research from the Insurance Institute for Highway Safety suggests that 12% of drivers are […]

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