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Exactly, so when I get in that car, I want to know the probability of dying. How do you compute this? By taking the number of crashes per kilometer, and multipl

Exactly, so when I get in that car, I want to know the probability of dying. How do you compute this? By taking the number of crashes per kilometer, and multiplying by the number of kilometers you'll drive for. A trip of 5000km is less safe than a 5km one. That's just common sense. Similarly, when comparing flying versus driving from Amsterdam to Paris, you are, as you say, interested in which method is most likely to get you to your destination alive. So you take the number of incidents per kilometer for planes and cars, and multiply them by the distance between Amsterdam and Paris. The interesting figure really is incidents / kilometer, that's just basic math.

DrScientist 2y ago
However the risks aren't necessarily proportional to miles travelled. So for example with flights - I'd imagine the most dangerous parts are the take-off and landing - which happen once per trip no matter how long you fly for inbetween. So for flights incidents / kilometer are perhaps misleading.
- castlestripe 2y ago
  Fatalities per trip is similarly misleading because of the number of extremely short trips people make in cars. If you really start including risk factors you'll never stop, the risk is proportional to many other factors as well: 1) Time of day: Time of day factors in probably for both flying and driving at varying degrees 2) Where: In the US, which state you're driving in matters significantly for driving fatality rates 3) Day of week: Driving on weekends is more dangerous than driving during the week, doesn't seem to affect flights 4) ATC is a variable for flight accidents but not drivers 5) Flights might actually carry more risk per mile in certain situations: Flying over the oceans, eg A truly correct apples-to-apples comparison would be so hyper-specific as to be useless.
  - DrScientist 2y ago
    The other key point when comparing car stats to flights is car stats include pedestrian/cyclist and motorcyclist deaths which make up perhaps around half of the deaths. Yet I suspect the people in twin towers weren't included in airline death stats. Sure there isn't a perfect single metric - just pointing out that the one the airlines prefer appears to be biased towards air-travel. The other factor that is often ignored is the issue of control. As a passenger of an airline you have very little impact on the chance of an accident - you are just an accident statistic. Whereas if you are driving, your own driving behaviour, choice of car, route etc puts you more in control of the chances ( though of course by no means completely ). This has a big impact on the perception of risk ( as more than average think they are better than average :-) ).
_heimdall 2y ago
> taking the number of crashes per kilometer, and multiplying by the number of kilometers you'll drive for. A trip of 5000km is less safe than a 5km one. When comparing a difference of 1000x, sure its probably safer. Your premise is wrong though, it isn't common sense to take a generalized statistic like deaths per km and extrapolate that to be the correct estimate for any particular trip. The statistic loses all context of differences in vehicles, road conditions, time of day, specific roads, etc. The stat is a great example of how a statistic seems meaningful to get a big picture but is completely useless to us as we can't make any decisions based on a number that is so generalized as to lose all context and meaning.
- berndi 2y ago
  Common sense means taking the less risky option. Assuming that the survival rate is constant as a function of trip length, the empirical estimate of the risk is fully determined by the number of deaths per distance.
  - sokoloff 2y ago
    In this case, they’re not fully determined by distance. Airline travel is much riskier in takeoff and landing phases. A bunch of 200 mile flights is riskier than a 3500 mile trans-con trip. Car travel is much safer on controlled access highways than 40 mph surface streets.
  - _heimdall 2y ago
    > Assuming that the survival rate is constant as a function of trip length That's an assumption that doesn't hold up, at least that's the argument I was trying to make above. Generalizing so much data down to a single statistic makes the number useless. Almost all context is lost, really the only context kept is mode of transportation and distance traveled. That isn't enough to help anyone make a decision for any particular trip.
croes 2y ago
So if I take two 100km trips by car, one takes 30 minutes and the other 2 hours both are equally safe?

DrScientist 2y ago

However the risks aren't necessarily proportional to miles travelled. So for example with flights - I'd imagine the most dangerous parts are the take-off and landing - which happen once per trip no matter how long you fly for inbetween. So for flights incidents / kilometer are perhaps misleading.

castlestripe 2y ago
Fatalities per trip is similarly misleading because of the number of extremely short trips people make in cars. If you really start including risk factors you'll never stop, the risk is proportional to many other factors as well: 1) Time of day: Time of day factors in probably for both flying and driving at varying degrees 2) Where: In the US, which state you're driving in matters significantly for driving fatality rates 3) Day of week: Driving on weekends is more dangerous than driving during the week, doesn't seem to affect flights 4) ATC is a variable for flight accidents but not drivers 5) Flights might actually carry more risk per mile in certain situations: Flying over the oceans, eg A truly correct apples-to-apples comparison would be so hyper-specific as to be useless.
- DrScientist 2y ago
  The other key point when comparing car stats to flights is car stats include pedestrian/cyclist and motorcyclist deaths which make up perhaps around half of the deaths. Yet I suspect the people in twin towers weren't included in airline death stats. Sure there isn't a perfect single metric - just pointing out that the one the airlines prefer appears to be biased towards air-travel. The other factor that is often ignored is the issue of control. As a passenger of an airline you have very little impact on the chance of an accident - you are just an accident statistic. Whereas if you are driving, your own driving behaviour, choice of car, route etc puts you more in control of the chances ( though of course by no means completely ). This has a big impact on the perception of risk ( as more than average think they are better than average :-) ).

_heimdall 2y ago

> taking the number of crashes per kilometer, and multiplying by the number of kilometers you'll drive for. A trip of 5000km is less safe than a 5km one. When comparing a difference of 1000x, sure its probably safer. Your premise is wrong though, it isn't common sense to take a generalized statistic like deaths per km and extrapolate that to be the correct estimate for any particular trip. The statistic loses all context of differences in vehicles, road conditions, time of day, specific roads, etc. The stat is a great example of how a statistic seems meaningful to get a big picture but is completely useless to us as we can't make any decisions based on a number that is so generalized as to lose all context and meaning.

berndi 2y ago
Common sense means taking the less risky option. Assuming that the survival rate is constant as a function of trip length, the empirical estimate of the risk is fully determined by the number of deaths per distance.
- sokoloff 2y ago
  In this case, they’re not fully determined by distance. Airline travel is much riskier in takeoff and landing phases. A bunch of 200 mile flights is riskier than a 3500 mile trans-con trip. Car travel is much safer on controlled access highways than 40 mph surface streets.
- _heimdall 2y ago
  > Assuming that the survival rate is constant as a function of trip length That's an assumption that doesn't hold up, at least that's the argument I was trying to make above. Generalizing so much data down to a single statistic makes the number useless. Almost all context is lost, really the only context kept is mode of transportation and distance traveled. That isn't enough to help anyone make a decision for any particular trip.

croes 2y ago

So if I take two 100km trips by car, one takes 30 minutes and the other 2 hours both are equally safe?