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Comment by jessriedel | Hacker News Reader

What's the back of the envelope on whether the 737 Max is more dangerous than driving?

1,300 aircraft have been built since the first started flying in 2017, with two deadly crashes. I don't know how many miles those have accumulated, but presumably it's of order 4k miles per day per aircraft, and maybe 3 years (1000 days) of flying to date per aircraft on average, giving a very rough estimate of a few billion miles? So maybe a deadly crash per billion miles, in comparison to a bit over one deadly crash per 100M miles for cars.

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Who cares? The age-old comparison against cars is just to illustrate that flying, on average, is safer than driving, which most people intuitively don’t “feel” to be true (or at least they didn’t back in the days).

In this case we’re talking about a company that consistently makes mistakes and puts their passengers lives at risk due to negligence, whether “it’s still safer than driving” or not is completely irrelevant, because what they’re doing is not OK no matter how much safer it is than driving.

It helps me tell if I should personally care about this. (There are people in this talking about how they would never get on one of these planes, etc.) It also is informative for how much public attention its worth.

> maybe 3 years (1000 days) of flying to date per aircraft on average

It's probably a lot less. 950 out of those 1300 aircraft were delivered in the last three years, and the other 350 were grounded throughout most of 2019 and 2020.

Cool, thanks. So probably a factor of ~2 fewer miles, or twice the accident rate.

divide by the # of passengers...

Not really necessary. The two accidents killed everyone on board, and it was a typical load. The number I estimated is something like "fatal crash for everyone per mile". You could multiply by average of passengers on each flight and divide by the average number of passengers on the deadly flights to get a slightly more accurate risk, but not much would change.

You can’t compare like that.

If you drive into a tree and get maimed, it’s different to someone else driving you into a tree and maiming you.

When you’re welfare is in someone else’s hands, they need to better than you would.

I wasn't drawing an equivalence, moral or otherwise

> What's the back of the envelope on whether the 737 Max is more dangerous than driving?

Driving is an absurdly dangerous mode of transportation, so it’s probably not the best comparison.

It's the one most Americans use everyday, so it tells us about the risks that most people find accessible for the benefit they get.

Perhaps on an individual level, but on a policy level, it makes sense that the safety standards for flying are higher for flying than for driving.

I sort of agree. There is some cost-safety trade-off curve, and it's almost certainly true that you can get more safety for less cost/hassle on airplanes (or any large-group travel) than private cars. So in that sense, yes, the optimal amount of safety will be higher for planes.

However, I think we should still respect individual preferences for safety in the sense that public transit should try and make the trade-offs individuals would make according to their values. In practice that means trying to estimate the value individuals put on safety through their revealed preferences, with cars being a key example. Although there are some choices the FAA makes here that a smart, on some other choices I think they impose hassles on passengers that aren't remotely justified by the safety benefit, e.g., mandatory seat belt use.

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