Flawed study of distracted driving

The Robert Wood Johnson Foundation funded, and researchers at the University of Nebraska have conducted, a study of fatalities due to distracted driving, Fatalities of Pedestrians, Bicycle Riders, and Motorists Due to Distracted Driving Motor Vehicle Crashes in the U.S., 2005–2010. It is online, here.

The report offers some interesting information, but it can very easily be misinterpreted, oddly excludes fatalities to distracted drivers themselves, and draws some unsupported conclusions about bicycling safety.

Nobody with any familiarity with the bicycling research literature would use the term “Bicycle Riders.” OK, that’s a nitpick but it gets better.

This is in the abstract:

Bicycling victims of distracted crashes were disproportionately male, non-Hispanic white, and struck by a distracted driver outside of a crosswalk.

This duplicates the wording for pedestrians and implies that bicyclists normally ride on sidewalks and in crosswalks.

The abstract also states, without qualification:

The rate of fatalities per 10 billion vehicle miles traveled increased from 116.1 in 2005 to 168.6 in 2010 for pedestrians and from 18.7 in 2005 to 24.6 in 2010 for bicyclists.

No such increase of approximately 30% in bicyclist and pedestrian fatalities has been seen. Why? Because, as the text on page 437 indicates, these numbers apply only to crashes due to distracted driving. There are many other crashes, and the rate of those has been going down.

Also, oddly, the study does not count fatalities to distracted drivers themselves. This is in a footnote to Figure 3, on page 439:

Motorist fatalities include motor vehicle passengers and non-distracted drivers involved in a distracted driving-related crash. Drivers who were distracted and died in the crash were excluded.

As the text of the report describes, only “victims” were counted. Why? The distracted drivers died too.

Statistics on drunk driving count everyone who died including the drunk drivers. Now, there may be a reasonable explanation for a different method with distracted driving: that it is harder to determine whether a dead person had been distracted, than drunk. But the report doesn’t explain this. In any case, it should be possible to arrive at a good estimate based on other data, and we don’t get a true picture of the extent of the problem unless we count everyone.

And, about countermeasures:

Thus, our findings highlight the need for policy solutions emphasizing primary prevention of driving while distracted. Potential solutions may include implementing clear and lighted crosswalk markings, constructing sidewalks, and creating separate bicycle lanes with barriers to separate bicyclists from traffic.

The recommendation about bicycling is a typical “knee jerk” recommendation from researchers who have no expertise about bicycling. Aside from the fact that a bike lane, by definition, is not behind a barrier, the report cites exactly two recent studies by advocates for separate bicycle facilities — whose focus is primarily on increasing mode share by creating the appearance of safety — with no reference to the larger body of research literature which indicates higher crash rates for such designs. As usual in epidemiological studies, there is no examination of crash causation. An examination of the patterns of crash types when distracted driving is involved, compared with other crashes, would certainly be helpful, but there is none here.

13 responses to “Flawed study of distracted driving

  1. how many motorists do you opine died in pedestrian and bicyclist -motor vehicle accidents, John?

    can you glean that number out of the FARS data for us?

  2. Dan, whoever you are — could you use your real name please? — this looks like a hostile comment, but I’m posting it and I’ll answer it.

    The study examined crashes in which distracted driving was identified as a contributing factor in a fatality. It counted victims of other people’s distracted driving, including their passengers and people in other motor vehicles, as well as bicyclists and pedestrians. But the study did not count, or even give an explanation for not counting, motorists who died due to their own distracted driving. Without this, we don’t have a good handle on the problem or an appropriate warning for drivers.

    The number for motorists who died in collisions with bicyclists and pedestrians could be deduced from the FARS data. Why should I have to do that? To claim some kind of moral superiority in victimhood? We all know that the number is very low. Bicyclists and pedestrians are more vulnerable than motorists, but what if anything does that have to do with the U. of Nebraska study, or my critique of it?

  3. I just sent this to John the the first author:

    John, thanks for posting the link to the U of Nebraska distracted driving study. I do have a couple of quick questions for the authors, after a very quick scan of the article.

    One, the startling decrease in motorist fatalities due to distracted driving while at the same time seeing an increase in ped and bike fatalities attributed to distracted driving (~33%) is, according to the authors, due to better car crashworthiness. Are we sure none of this is due to reporting?

    I’d like to have seen a graph of total crashes per year attributed by the authorities to distracted driving, because I would hazard a guess that the numbers of total crashes should be increasing in proportion to numbers of text messages, and to follow a similar curve to the increase in bike and ped fatalities. One could then surmise that if total crashes are going up but motorist deaths due to distraction decreasing, perhaps it’s the protection of the vehicle rather than problems with reporting.

    Two, if I were going to argue for separated bike facilities and better crosswalk design on the basis of this study, I’d liked to have seen some compilation of data showing what type of fatal car-bike crashes are causing these deaths and what sort of crosswalk designs will jolt a distracted motorist back to attention. If, for example, more cyclists passing through intersections are being hit by motorists failing to yield, then a separated bike facility won’t do much good within the intersection. If these are all hit from behind (sensu lato) crashes due to failure to maintain lane or to distracted motorist overtaking and slamming into someone due to speed differentials, then one could better argue for separation between intersections (which requires intersection control be installed due to these segregated facilities requiring their own right of way cycles). I don’t see the data to support such an analysis.

    The bigger issue is that there are far more motorists out there than pedestrians and bicyclists, and everyone is at greater risk from distracted driving as we keep finding ways to distract drivers. I’d attack the distraction first.

    I’ll give this a deeper read later on when I get some laboratory work done with my paying job….

    • The startling decrease in motorist fatalities can’t be due to crashworthiness. The motor-vehicle fleet doesn’t turn over fast enough and new features aren’t introduced fast enough to account for the decrease.

  4. So their logic goes as follows: distracted drivers are dangerous, but clearly we can’t do anything about that, so let’s protect the potential victims? We wouldn’t do this for other types of criminals except where the justice system has severely broken down.

    Rather than investing in magic crosswalks that somehow snap drivers to attention like a drill sergeant, maybe we could require cars to have less distractions, and possibly also enforce basic traffic laws. A distracted driver going 30km/h is much less likely to kill a pedestrian or cyclist than a distracted driver going 60km/h. It’s not like our technology isn’t advanced enough to make cars go slower, or to automatically punish those people who put others in danger by speeding.


  5. What Jean-Francois said. To some degree, that article sounds like the NRA version of traffic control: The only thing stopping a bad guy with a car is a good guy with an even bigger car. Everyone else should just get the hell outa the way.

    It should be technological possible to have interlocks on distracting devices that engage when the vehicle is in motion. Also possible to design systems that are not so distracting and prohibit those that are distracting, which the government, in theory, could do if it had the gumption. MV manufacturers have taken the opposite approach and will market increasingly complex goodies to motorists until someone stops them.

    Back a few years ago, I think it was Consumer Reports and Excellence Magazine that castigated BMW, in particular, for the confounding and distracting I-Drive control system on its electronic gadgetry. Now that seems to be the rule rather than the exception.

    By far, the more serious issue, other than blaming the technology, is that US drivers are so used to lax standards of personal responsibility that the smart phones and programmable auto entertainment systems are a symptom rather than the disease. Whether it be any form of distraction or just plain carelessness, the basic tenet of American driving is “what, me worry”?

  6. An obvious first step is to make using a cell phone inside a car that is being operated a “rebuttable presumption of negligence” in the event of any collision. The proposed paper solutions strike me as similar logic to mandating chastity belts as a solution to rape.

    • No, not chastity belts. Those would actually prevent the consummation of the rape. The equivalent in traffic engineering would be to wall off pedestrians and bicyclists entirely so they could never travel on streets, or cross them. The more accurate analogy which occurs to me is of women’s dormitories with dorm mothers like those at the college I attended back in the ’60s — system which broke down on weekends at the parties at fraternities at the bottom of the hill, where distraction was induced through the liberal consumption of alcohol.

    • Or, perhaps, this is similar logic to going back to segregated neighborhoods to ensure the safety of minority groups.

  7. As other people have suggested, the problem with their proposed solution is that being “distracted” is largely non-random. That is, there are some simple, common-sense steps that help driving attentiveness.

  8. I find it surprising that educated professionals would actually put their name to this ” study” and its conclusions. The study also supports the conclusion that motorists “text less” or, “focus on the road” more when expecting conflicts, ie. when approaching intersections, especially those large enough to require crosswalks, while perhaps lowering their driving attention mid block and less urban settings. Too much information is missing to draw any credible conclusions and support fortified crosswalks and cycle lanes.

  9. it doesn’t have to even be talking on the phone or texting. You could be reaching for something, trying to peek at directions, or anything that takes your attention away from the road. Yes, it’s possible to multi-task, but when you’re driving, there is so much to pay attention to, and the situation changes every second. Why risk it? Heck, I know someone who gets too distracted by books on tape, he gets too into the story and loses his focus. Not cool.

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