4 ms·

I'm surprised to see buses listed as being much safer per journey than trains. I guess that's just because "per journey" is a rather meaningless metric. Train j

by Tepix 7y ago

I'm surprised to see buses listed as being much safer per journey than trains. I guess that's just because "per journey" is a rather meaningless metric. Train journeys must be longer than bus journeys on average. However, even when you compare bus vs train on a death per billion km base, the bus is much safer (0.4 vs 0.6). Is it because on average buses travel slower than trains? How accurate are these numbers?

jacknews 7y ago
indeed, per-journey is entirely meaningless, per-hour is the correct measure of risk.
- rdtsc 7y ago
  A journey seems like a meaningful unit of work here. Sometimes the start or end of a journey is more dangerous. The decision to even start journey would look at the per journey risk perhaps. Think of space launches, as an extreme example. Risk per distance or per hour, if you consider orbiting for a while, could be low but risk per journey quite high.
  - jacknews 7y ago
    The point is the different modes have entirely different profiles. You don't fly to the supermarket, or walk to an exotic holiday location.
soneil 7y ago
I think a lot of these don't suffer direct comparisons well. eg, the greatest risk of accidents to a bus, comes from other passenger vehicles where the bus is more likely to win that particular dispute. The greatest risk of accidents to a train, comes from the trains own inertia, where the train is much more likely to lose. The greatest risk of accidents to an aircraft is the ground, in which the ground has an undisputed record. So I think it's safe to assume busses would be more likely to have accidents, but less likely to have fatalities. I think it actually gets worse if you try to normalise the results. There is greater risk in a car journey from LAX to JKF, than there is for an air journey along the same route. However, if I tried to commute by air to work (a 2km commute), the risk per km would rocket, as take-offs and landings are the most dangerous part of each journey, so with an atypical number of take-offs per km, I'd get an atypical risk per km. The wiki article does go on to point out the difference in usage of these statistics. per-journey does make more sense for air insurance, as the difference in risk between long-haul and short-haul isn't really significant - the take-off and landing are still the riskiest phases, there's just a larger period of boredom between them for long-haul. So 10 short flights vs 1 10x longer flight might normalise to the same hours & kms, but 10 short flights means 10 landings etc (10x the chances to miscalculate fuel, 10x the entries into & out of congested airspace, etc) But comparing per-journey between a car and a plane is rather meaningless, as they are on average very different journeys. commuting in a car isn't two phases of high risk separated by one phase of near-immunity.

by Tepix 7y ago

jacknews 7y ago

indeed, per-journey is entirely meaningless, per-hour is the correct measure of risk.

rdtsc 7y ago
A journey seems like a meaningful unit of work here. Sometimes the start or end of a journey is more dangerous. The decision to even start journey would look at the per journey risk perhaps. Think of space launches, as an extreme example. Risk per distance or per hour, if you consider orbiting for a while, could be low but risk per journey quite high.
- jacknews 7y ago
  The point is the different modes have entirely different profiles. You don't fly to the supermarket, or walk to an exotic holiday location.

soneil 7y ago

I think a lot of these don't suffer direct comparisons well. eg, the greatest risk of accidents to a bus, comes from other passenger vehicles where the bus is more likely to win that particular dispute. The greatest risk of accidents to a train, comes from the trains own inertia, where the train is much more likely to lose. The greatest risk of accidents to an aircraft is the ground, in which the ground has an undisputed record. So I think it's safe to assume busses would be more likely to have accidents, but less likely to have fatalities. I think it actually gets worse if you try to normalise the results. There is greater risk in a car journey from LAX to JKF, than there is for an air journey along the same route. However, if I tried to commute by air to work (a 2km commute), the risk per km would rocket, as take-offs and landings are the most dangerous part of each journey, so with an atypical number of take-offs per km, I'd get an atypical risk per km. The wiki article does go on to point out the difference in usage of these statistics. per-journey does make more sense for air insurance, as the difference in risk between long-haul and short-haul isn't really significant - the take-off and landing are still the riskiest phases, there's just a larger period of boredom between them for long-haul. So 10 short flights vs 1 10x longer flight might normalise to the same hours & kms, but 10 short flights means 10 landings etc (10x the chances to miscalculate fuel, 10x the entries into & out of congested airspace, etc) But comparing per-journey between a car and a plane is rather meaningless, as they are on average very different journeys. commuting in a car isn't two phases of high risk separated by one phase of near-immunity.