London is an exceptionally unsafe place for cyclists. I doubt it’s anywhere near so unsafe as to make up all the difference between cycling and driving in those statistics, but I would guess it’s at least 10x worse than the average, maybe quite a bit more.
… Ah, wait, I see you have other statistics saying 35 deaths per billion miles cycled, which would be about 21 per billion km, versus 11 per 100k km or 110,000 per billion km in London. So, apparently London is nearly four orders of magnitude worse than average. That’s … more than I expected. Have I misunderstood or miscalculated something?
That “11 per 100k km” figure says that if someone has a 2x5km commute in London that they do 200 days per year, they expect to die about 0.22 times per year; in other words, their life expectancy is a bit less than 5 years. I repeat, London is exceptionally unsafe for cyclists, but I think I’m going to defy the data here. Can it really be that unsafe?
[EDITED to add:] Some other figures I’ve seen suggest that serious injuries are maybe 20x as common as deaths. That means that my hypothetical 10km/day London cyclist should expect four serious injuries per year. Really?
There are some statistics on the Wikipedia Cycling in London page. For 2014 they report 13 deaths from 610k “daily journeys”. Even if a “daily journey” is as short as 1km, that would be 13 deaths per 610k km, which is a lot less than 11 per 100k km. (Though still scandalously large.)
FWIW (a year later) I read the statistic the same way you initially did, but didn’t do the comparison. Sorry! Thanks for doing the maths below and in the edit.
The paper is doing some weird things. To quote from it:
Fatality rates are difficult to obtain as there is no estimate of the miles cycled per year. We have compromised by providing the fatality rates per 100,000 estimated cyclists per kilometre on the roads of London. However, for an individual cyclist, it would be more useful to know the fatality rate per million miles cycled—a figure that currently cannot be obtained.
No, per 100k cyclists per kilometre; that is, per 100k cyclist-kilometres, which is dimensionally correct. Or am I misunderstanding what it is you find weird?
I only glanced at the paper, but my suspicion is that they are using something like 100K cyclists per kilometre of road, not per kilometre actually cycled. They admit to not knowing the miles cycled, but if you guesstimate the number of cyclists and you know the length of roads in London, you can produce a “cyclists per kilometre of road” metric. I am not sure how meaningful it is.
Cyclists per kilometre of road is a measure of cyclist density. To do a proper density estimate you also need to know how long (in hours) does an average cyclist spend on the road, but conceivably you can handwave it away as a near-constant. Given this, their approach is to look at the fatalities as a function of the cyclist density.
They are still missing too many variables to produce a useful estimate, but it’s not prima facie insane.
Yes it is prima facie insane, because the number of fatalities should look like f(density) times quantity of road (or quantity of cycling or something). Maybe they kinda get away with it when comparing fatalities across years, because the quantity of road doesn’t change much—but that would equally justify measuring quantity of cycling as, say, “number of cyclists divided by latitude” or “number of cyclist-kilometres times number of letters in city name”. So, good try, but I still think it’s obviously bonkers.
A foolish consistency is the hobgoblin of PEOPLE WHO NEED THEIR HEADS EXAMINED—GJMerson.
[EDITED to add:] Anyway, unless I’m misunderstanding your “Tony Stark” comment I don’t get the impression that you really find their use of that statistic very defensible.
Should I argue with this or no? Ah, a nice Catch-22… :-)
However there wasn’t much arguing in this thread. I didn’t tell gjm that he was wrong. Instead I offered more of an alternate explanation (to the “prima facie insane” hypothesis :-D) as I am generally interested in finding alternate ways of looking at things.
Once someone was saying that “you always say I’m wrong,” and I said, “I said you were right on occasions A, B, and C,” and they responded, “See! you’re doing it again! that proves you always say I’m wrong!”
Deaths per cyclist per kilometre of road is a crazy unit of measurement. I mean, sometimes you have to report the statistic you’ve got rather than the statistic you’d like, but I don’t see what possible practical significance this has.
The statistic we’d like to know is deaths per kilometre cycled. The average person in the UK cycles about 60 km a year (source: Department for Transport) and the population of London is about 8.5 million (source: Wikipedia), so the 19 deaths in 2006 correspond to about 3.5 deaths per 100 million kilometres cycled.
This is slightly higher than the UK average of 3.1 deaths per 100 million kilometres cycled, and on the high side for Western Europe (compare Netherlands: 1.0; Germany: 1.8; France: 3.1; Italy: 3.4).
London is an exceptionally unsafe place for cyclists. I doubt it’s anywhere near so unsafe as to make up all the difference between cycling and driving in those statistics, but I would guess it’s at least 10x worse than the average, maybe quite a bit more.
… Ah, wait, I see you have other statistics saying 35 deaths per billion miles cycled, which would be about 21 per billion km, versus 11 per 100k km or 110,000 per billion km in London. So, apparently London is nearly four orders of magnitude worse than average. That’s … more than I expected. Have I misunderstood or miscalculated something?
That “11 per 100k km” figure says that if someone has a 2x5km commute in London that they do 200 days per year, they expect to die about 0.22 times per year; in other words, their life expectancy is a bit less than 5 years. I repeat, London is exceptionally unsafe for cyclists, but I think I’m going to defy the data here. Can it really be that unsafe?
[EDITED to add:] Some other figures I’ve seen suggest that serious injuries are maybe 20x as common as deaths. That means that my hypothetical 10km/day London cyclist should expect four serious injuries per year. Really?
There are some statistics on the Wikipedia Cycling in London page. For 2014 they report 13 deaths from 610k “daily journeys”. Even if a “daily journey” is as short as 1km, that would be 13 deaths per 610k km, which is a lot less than 11 per 100k km. (Though still scandalously large.)
FWIW (a year later) I read the statistic the same way you initially did, but didn’t do the comparison. Sorry! Thanks for doing the maths below and in the edit.
The paper is doing some weird things. To quote from it:
Note: cyclists per kilometre.
No, per 100k cyclists per kilometre; that is, per 100k cyclist-kilometres, which is dimensionally correct. Or am I misunderstanding what it is you find weird?
I only glanced at the paper, but my suspicion is that they are using something like 100K cyclists per kilometre of road, not per kilometre actually cycled. They admit to not knowing the miles cycled, but if you guesstimate the number of cyclists and you know the length of roads in London, you can produce a “cyclists per kilometre of road” metric. I am not sure how meaningful it is.
Bloody hell, you appear to be right. What a ridiculous figure to be publishing.
I am quite sure how meaningful it is: not meaningful at all.
Paging Tony Stark! :-)
Cyclists per kilometre of road is a measure of cyclist density. To do a proper density estimate you also need to know how long (in hours) does an average cyclist spend on the road, but conceivably you can handwave it away as a near-constant. Given this, their approach is to look at the fatalities as a function of the cyclist density.
They are still missing too many variables to produce a useful estimate, but it’s not prima facie insane.
Yes it is prima facie insane, because the number of fatalities should look like f(density) times quantity of road (or quantity of cycling or something). Maybe they kinda get away with it when comparing fatalities across years, because the quantity of road doesn’t change much—but that would equally justify measuring quantity of cycling as, say, “number of cyclists divided by latitude” or “number of cyclist-kilometres times number of letters in city name”. So, good try, but I still think it’s obviously bonkers.
Funny how the usual roles reversed: I get charitable and you go THESE PEOPLE NEED THEIR HEAD EXAMINED :-D
A foolish consistency is the hobgoblin of PEOPLE WHO NEED THEIR HEADS EXAMINED—GJMerson.
[EDITED to add:] Anyway, unless I’m misunderstanding your “Tony Stark” comment I don’t get the impression that you really find their use of that statistic very defensible.
The actual explanation for this is your desire to argue with your current interlocutor, whoever that may be at the moment.
Should I argue with this or no? Ah, a nice Catch-22… :-)
However there wasn’t much arguing in this thread. I didn’t tell gjm that he was wrong. Instead I offered more of an alternate explanation (to the “prima facie insane” hypothesis :-D) as I am generally interested in finding alternate ways of looking at things.
Once someone was saying that “you always say I’m wrong,” and I said, “I said you were right on occasions A, B, and C,” and they responded, “See! you’re doing it again! that proves you always say I’m wrong!”
Deaths per cyclist per kilometre of road is a crazy unit of measurement. I mean, sometimes you have to report the statistic you’ve got rather than the statistic you’d like, but I don’t see what possible practical significance this has.
The statistic we’d like to know is deaths per kilometre cycled. The average person in the UK cycles about 60 km a year (source: Department for Transport) and the population of London is about 8.5 million (source: Wikipedia), so the 19 deaths in 2006 correspond to about 3.5 deaths per 100 million kilometres cycled.
This is slightly higher than the UK average of 3.1 deaths per 100 million kilometres cycled, and on the high side for Western Europe (compare Netherlands: 1.0; Germany: 1.8; France: 3.1; Italy: 3.4).