Cell phone use increases the risk of traffic accidents right? But how do we prove that? By showing that a large fraction of accidents involve people talking on cell phones? Not enough. A huge fraction of accidents involve people wearing shoes too.
I thought about this for a while and short of a careful randomized experiment it seems hard to get a handle on this using field data. I poked around a bit and I didn’t find much that looked very convincing. To give you an example of the standards of research on this topic, one study I found actually contains the following line:
Results Driver’s use of a mobile phone up to 10 minutes before a crash was associated with a fourfold increased likelihood of crashing (odds ratio 4.1, 95% confidence interval 2.2 to 7.7, P < 0.001).
(Think about that for a second.)
Here’s something we could try. Compare the time trend of accident rates for the overall population of drivers with the same trend restricted to deaf drivers. We would want a time period that begins before the widespread use of mobile phones and continues until today. Presumably the deaf do not talk on cell phones. So if cell phone use contributed to an increase in traffic risk we would see that in the general population but not among the deaf.
On the other hand, the deaf can use text messaging. Since there was a period of time when cell phones were in widespread use but text messaging was not, then this gives us an additional test. If text messaging causes accidents, then this is a bump we should see in both samples.
Anyone know if the data are available? I am serious.
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September 28, 2010 at 11:14 pm
David Shor
The whole instrumental variable approach involving the deaf and technological change is cute, but not terribly convincing.
Barabasi(Network theory guy), used a large database that tracked thousands of cell-phones every couple of minutes and probably had call tags. I would try to develop some heuristics that identify accidents (Stops on highways, or worse, stops on highways that then go to the hospital/destroy the phone), and correlate with talk time.
Or if the IV approach is needed, correlate sudden spikes in cell-phone talking with instantaneous accident rates. For example, night and weekend minutes suddenly apply at 7pm for some carriers, even if it’s bright out due to DST.
September 28, 2010 at 11:17 pm
itovertakesme
If we don’t observe an overall increase in accidents compared with deaf people, how should we reinterpret the positive correlation between cell phone use and traffic accidents? In other words, what is the competing theory you are testing? People who use cell-phones when driving are fundamentally a more accident-prone group of people which is unaffected by their cell-phone use? (E.g. they are busy distracted drivers whether they talk on the phone or not?)
September 29, 2010 at 10:36 am
jeff
If there is such a correlation then yes it would be that cell-phone use is correlated with something else that increases accident risk. you are younger, you drive more and in different places. (but in fact my bet would be that we would see a difference between the deaf and the general population.)
September 28, 2010 at 11:41 pm
jasdeephundal
Cell phone adoption rates vary by region/country, so I wonder if this could possibly provide useful data. Then again, traffic laws and attitudes to driving vary by country, but I choose to throw this idea out there anyways.
September 29, 2010 at 1:03 am
rd
did you see these?
http://www.bepress.com/bejeap/advances/vol6/iss1/art9/
http://www.bepress.com/bejeap/vol9/iss1/art10/
only read abstracts but the first one directly addresses selection issue
September 29, 2010 at 10:32 am
jeff
thanks very much rd. i am looking at these.
September 29, 2010 at 4:37 am
Mike
I thought this identification strategy seemed somewhat convincing when I first heard about it:
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1089081
September 29, 2010 at 10:32 am
jeff
thank you!
September 29, 2010 at 4:23 pm
WillJ
I think the study you’re making fun of actually does settle the question:
“Results: Driver’s use of a mobile phone up to 10 minutes before a crash was associated with a fourfold increased likelihood of crashing (odds ratio 4.1, 95% confidence interval 2.2 to 7.7, P < 0.001)."
Yes, that sentence is retarded, but I think what they meant to say is that people were four times more likely to be using a cell phone within a period up to 10 minutes before crashing than to be using a cell phone during control periods when they didn't crash.
If that's the case, then actually I think that's pretty good evidence of the danger of cell phones, at least if their simple interrogation technique ("Did you use a cell phone between Time X and Time Y?") is OK and their control time periods are valid (they claim to have chosen comparable times). Since they're comparing people with themselves at different times, rather than different groups of people, that rules out your explanations involving age, driving more, etc. The only plausible explanation remaining, as far as I can tell, is that, indeed, cell phones impair driving ability.
June 10, 2013 at 9:23 am
Gloria
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September 30, 2013 at 5:41 am
Chelsi
business insurance
October 17, 2013 at 4:23 pm
Reignbeau
Smart thkniing – a clever way of looking at it.
October 12, 2010 at 11:05 pm
Distracted Driving Followup « Cheap Talk
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