Saturday, June 20, 2009

i believe i can fly

It doesn't take much to get me musing fearfully about air travel, and the recent Air France disaster has provided some food for thought. Let me sneak up on this in a slightly tangential way.

I read an interesting article the other day about airport security - most of us instinctively know that it's largely a meaningless pantomime designed to give the illusion of safety to those who haven't really thought it through, and for the authorities to be seen to be "doing something" to address a nebulous and badly-defined threat with an ill-understood degree of risk attached to it (on top of the fact that most people fail to understand the level of risk inherent in getting on a plane anyway, terrorists or no terrorists: more on that in a minute), but the article nails some of the specifics in an interesting way.

The journalist who wrote the article enlisted the assistance of Bruce Schneier, who is generally acknowledged as being the man to talk to about all things security-related. Schneier started out as a computer cryptography expert, but now seems to be a sort of general purpose guru-for-hire on all subjects, including airline security, post-9/11 in particular. He also has a website with lots of stuff that even those not interested in, say, collision attacks on MD5 hash algorithms (and my day job requires me to be at least partially interested in that sort of stuff) may find interesting, for instance this essay about the psychology of security. A lot of thought-provoking material about our ability to assess risk, and the ways in which we often make profoundly irrational decisions when doing so; one interesting point is the notion that the speed of technological progress and the rate at which it throws up new and previously unknown risks to be dealt with has become so rapid as to outpace our ability to evolve proper strategies to respond to those risks. Consequently relying on "instinct" or "gut feeling" to tell you the right thing to do is likely to result in the wrong decision being made, with potentially disastrous consequences.

Inevitably the essay touches on airport security; it also briefly touches on the relative risks of air travel and car travel. This is a fascinating subject and an interesting example of the old saw about statistics. Any safety figures you see presented by the aviation industry will tell you that air travel is something like 60 times safer than car travel. Well, that sounds pretty safe; I mean, I've never died in a car crash, and that's far more dangerous than flying! Trouble is these figures are based on a "deaths by passenger mile travelled" calculation. Ask yourself this: is a plane journey in which you travel 5000 miles and arrive safely 100 times safer than a car journey in which you travel 50 miles and arrive safely (or, conversely: is a plane journey in which you travel 4900 miles and then crash and die 100 times safer than a car journey in which you travel 49 miles and then crash and die)? I'll help you out if you like, the answer is no, they are equally safe - arriving safely is the only meaningful criterion. On that basis if you redo the calculations on a "deaths by number of journeys taken" basis you come up with a different answer, which is that air travel is about three times as dangerous as car travel. Granted, it's still something like 14 times safer than getting on a motorbike, but it gives you a different perspective on the subject. Insurance companies use the journey-based calculation, incidentally, and they know the score risk-wise if anyone does.

We're approaching the central subject here, which is my dislike of flying. This excellent article explains the issues extremely well so I won't regurgitate it all here, except to observe that the author has made the decision not to fly at all based on his conclusions. I don't quite go that far, as I make the judgment that my desire to visit far-flung places without having to spend three weeks on a boat outweighs my aversion to flying, but I still have a violent fear and loathing of the whole experience. And don't bother trying to explain how irrational my fear is. It's extremely rational.

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