Transportation Economics [Math Fixed]

Suppose that it’s 1 January 2001, and you know that at some point in the next 12 months terrorists will take down four airplanes, killing more than 500 passengers. You have a job that requires you to travel from Houston to Newark at least once and up to twelve times. By road, you live 20 miles from the Houston airport and work 10 miles from the Newark airport.

Which would be the safer travel plan?:

  • To drive once; or
  • To fly twelve times?

(Never mind the added danger of being murdered in Newark, or of slipping and falling in an unfamiliar hotel tub. We’re just talking transportation safety.)

In 2001, by far the most dangerous year in recent history for U.S. commercial aviation, there were 0.85 fatalities per million passenger emplanements and .0096 fatalities per million highway passenger miles.

It’s a 3,242 mile driving round trip. So each time you drive you’ve got a 31-in-a-million (3,242 × .0096) chance of dying on the highway.

If you decide to fly, you still have to take highways to and from the airport. For each flying trip you will have had a 0.58-in-a-million (60 × .0096) chance of dying on way to or from airport, and a 1.7-in-a-million chance (2 × .85) of dying on a flight, for a total 2.3-in-a-million chance of dying on each trip.

So driving between Houston and Newark is statistically 13 times as dangerous, even in 2001, as flying. Yet Americans are content with the state of getting on the freeway, and happy to give up our privacy and our dignity if we think it’ll make flying safer.

As long, I suppose, as there’s no math.

(Statistics from various sources: fatalities per 100 million vehicles; highway passenger loads; passenger emplanements; aviation fatality statistics.)

4 responses to “Transportation Economics [Math Fixed]”

  1. I think you have a calculation error. You quote the airline fatality rate as “0.85 fatalities per million passenger emplanements” but later you describe the risk of a round-trip as “a 1.2-in-a-million chance (2 × .58) of dying on a flight.” I think you meant .85, not .58. By my calculations, this lowers the relative risk to about 13.7, which doesn’t affect the main point of your argument, although it does technically make flying 15 times slightly more dangerous.

  2. I would rather die driving then have some dude that speaks broken english feeling my man-sausage, sorry. Just the way I feel regarding not giving up my rights to travel the way I feel protects my privacy.

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