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There are interesting stats from TfL in London. Women make approximately 25% of bicycle trips in London, but account for about 40% of the fatalities. Yet when y

There are interesting stats from TfL in London. Women make approximately 25% of bicycle trips in London, but account for about 40% of the fatalities. Yet when you compare KSI (killed or seriously injured) by gender, men are more likely to be KSI for a given distance travelled. It's hard to interpret these statistics. I suspect there are significant behavioural differences, such as riding at different times of day and at different speeds, which account for some of the differences.

quietbritishjim 4y ago
Sounds like a classic case of Simpson's paradox [1]. Here's how it could work, but I've made everything up so might not be true at all - it's just an example of how those numbers could exist: * KSI goes up far less than expected as the journey length goes up (less than linearly, and maybe even down slightly between some categories). That's because the longer journeys are made by much more experienced cyclists - by definition, a very unfit cyclist never cycles 25miles, for example. * But the category of very shortest journeys makes up by far the largest proportion of journeys, so a straight unweighted averages of KSI across journey length categories would give a very unrepresentative view. * Those women that do cycle tend to be in the lower journey length categories because on average, women are less physically fit. In other words, women would tend to be in the relatively more dangerous category of shorter journey length. It's not more dangerous because it's shorter - it's more dangerous because you had to be less fit to be in it in the first place. Again, note that the above is all made up. But it shows how you could get to the contrdictory-sounding stats of the parent comment. [1] https://en.wikipedia.org/wiki/Simpson%27s_paradox https://en.wikipedia.org/wiki/Simpson%27s_paradox
maerF0x0 4y ago
> there are significant behavioural differences And i would bet that normal characteristics of testosterone would explain a sizable portion of the difference.
drak0n1c 4y ago
Women have less bone density and less muscle mass than men. In an equivalent physical trauma situation they are more likely to be hurt than men, as both the physical reaction in the face of danger is less agile/powerful and the body is more fragile. Both of these apply even moreso when controlling a bicycle, because of the more direct control nuances and the greater force disparity (exposure to cars and obstacles around you).

quietbritishjim 4y ago

Sounds like a classic case of Simpson's paradox [1]. Here's how it could work, but I've made everything up so might not be true at all - it's just an example of how those numbers could exist: * KSI goes up far less than expected as the journey length goes up (less than linearly, and maybe even down slightly between some categories). That's because the longer journeys are made by much more experienced cyclists - by definition, a very unfit cyclist never cycles 25miles, for example. * But the category of very shortest journeys makes up by far the largest proportion of journeys, so a straight unweighted averages of KSI across journey length categories would give a very unrepresentative view. * Those women that do cycle tend to be in the lower journey length categories because on average, women are less physically fit. In other words, women would tend to be in the relatively more dangerous category of shorter journey length. It's not more dangerous because it's shorter - it's more dangerous because you had to be less fit to be in it in the first place. Again, note that the above is all made up. But it shows how you could get to the contrdictory-sounding stats of the parent comment. [1] https://en.wikipedia.org/wiki/Simpson%27s_paradox https://en.wikipedia.org/wiki/Simpson%27s_paradox

maerF0x0 4y ago

> there are significant behavioural differences And i would bet that normal characteristics of testosterone would explain a sizable portion of the difference.

drak0n1c 4y ago

Women have less bone density and less muscle mass than men. In an equivalent physical trauma situation they are more likely to be hurt than men, as both the physical reaction in the face of danger is less agile/powerful and the body is more fragile. Both of these apply even moreso when controlling a bicycle, because of the more direct control nuances and the greater force disparity (exposure to cars and obstacles around you).