Thursday, June 27, 2013

Friends Don't Let Friends Carpool

The AAA foundation measured cognitive distraction while driving and reported that having a passenger in the car is as dangerous as using a cell phone. On a scale of 1 to 5, a handheld cell phone caused a distraction level of 2.45, a passenger 2.33 and a hands-free phone 2.27. On top of this, distraction causes risk to a passenger as well as a driver, whereas the other side of the cell phone conversation can't be harmed by a driver's distraction.

Since the popular media ignores this risk, as a public service I present some guidelines:
  1. Avoid carpooling whenever possible. While there are some advantages (less traffic, pollution and loss of natural resources), it is worth putting lives of the driver, passengers and others at extra risk?
  2. If you do carpool, do not talk to each other except in case of emergency.
  3. If you need to talk, pull over to a safe place and turn off your engine before engaging in conversation.
Car manufacturers must share some of the blame by building cars with multiple seats and not physically separating the driver from the other passengers.

In the same study, the AAA foundation rated solving difficult math and verbal tasks at the top distraction level of 5. So some words of advice particularly for readers of this blog
Don't Drive and Derive


  1. If you read the actual AAA study, it turns out that the "passenger" was prevented from seeing the road. So the "passenger" conversation and the hands-free cell phone conversation are unsurprisingly similar. There is plenty of other empirical evidence that passengers aren't anything remotely like cell phone usage in terms of distraction.

    In real life, the point is: if you're a passenger in a car, quit talking when the driving conditions are difficult. Or just don't leave the house until self-driving cars are commercially viable.

  2. Besides the scale presumably being monotonic in likelihood of collision, do we know anything else about how these numbers translate into risk? For instance, if it's linear and we assume that most traffic accidents are minor (no damage to humans), having a score of 2.5 amortized over 3 carpoolers seems better than having an individual score of 1.

  3. That's why I only use my cellphone when biking, e.g. to discuss with the passenger on the handlebar.
    No car, no risk.

  4. Great advice. Next time I'll tell my 4 year old and 1 year old to walk or take their own car.

  5. But Lance, this study completely ignores the positive affects of passengers. When I fall asleep at the wheel, my wife (when she is awake), wakes me up just in time so I can swerve and avoid an accident. If we are both asleep, the children's shrieks help avoid accidents. This is something current mobile phones are no good at. It would be better if we facetimed/skyped/googlehanged-out where the other passengers could get a full view of the road and help you.

    But of course even this has its limitations. If you remember, a few years back there was this incident where a guy feeling sleepy put his RV on cruise and went to sleep in his cosy bed at the back. The cruise technology being primitive, he had an accident. Only a physical passenger could have prevented that.

  6. > If you remember, a few years back there was this incident where a guy feeling sleepy put his RV on
    > cruise and went to sleep in his cosy bed at the back.

    FYI, since this blog values/seeks truth and solid reasoning, FWIW:

    Also, as others mentioned above, studies about "passenger distraction" need to be defined / questioned carefully.

    For example, see Box 2 (page 2, "Is a conversation on a mobile phone any different from conversing with a passenger in the vehicle?") of the 2011 WHO report:

    And references 11-14 at:

  7. Commenters don't seem to get the sarcasm in the article.

  8. This is not a joke. I actually totaled my car deriving a few years ago. (No injuries though) And the proof I was thinking about turned out to be totally flawed!

  9. The first commenter made the relevant point. Real world passengers that aren't idiots are not as distracting as cell phones.

  10. Anonymous 11:03--Many real-world passengers are very young, and even if they can see out the window, aren't going to be able recognize a difficult driving situation. (My usual passengers, when asked to be quiet for a bit because driving is getting complicated, usually reply with "Why".)

  11. But perhaps the causal link is not so simple as the study suggests: Although often driven (or derivin') to distraction while behind the wheel, John von Neumann famously said of one of his many automobile accidents: "I was proceeding down the road. The trees on the right were passing me in orderly fashion at 60 miles per hour. Suddenly one of them stepped in my path."

  12. If you shouldn't think and drive, does that mean you can't drive while thunk?