Statistics and cycling safety
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  1. #1
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    Statistics and cycling safety

    Andrew Gelman has a good blog post, referring to a more detailed article by Thomas Krag on cycling and safety:






    Bottom line: the more people cycle, the safer it is to cycle.

    And if you include the health benefits of cycling as well as the risk of accidents, here's what you find:
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    Quote Originally Posted by Fredke
    And if you include the health benefits of cycling as well as the risk of accidents, here's what you find:
    So cycling to work reduces the probability of death from 100% to about 70%. A 30% chance of immortality sounds pretty good to me!

    (Yeah, I know ... that's not how to interpret the chart. The words "relative" and "risk" change the interpretation considerably!)
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    Quote Originally Posted by ukbloke
    So cycling to work reduces the probability of death from 100% to about 70%. A 30% chance of immortality sounds pretty good to me!
    Immortal cyclists gots angels lookin' out for 'em:

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    Quote Originally Posted by ukbloke
    Yeah, I know ... that's not how to interpret the chart. The words "relative" and "risk" change the interpretation considerably!)
    Interpretation not required. As presented, there's no other way to view that chart.

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    Quote Originally Posted by Fredke
    Bottom line: the more people cycle, the safer it is to cycle.
    So, the more frequently a driver climbs into his racing car, the safer racing becomes?

    I had no idea!

    Relative mortality risk?

    Nobody's getting out of here alive.

  6. #6
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    Quote Originally Posted by mohair_chair
    Interpretation not required. As presented, there's no other way to view that chart.
    Well, what does the relative refer to? If it is relative to mileage, then the ride to work people aren't safer, they are just safer per mile. Overall, they might still be more likely to die in a bike accident than low mileage folks.

    These studies tell us something we already know - people who do something frequently do it better than those who don't. But riding more doesn't make you "safer", unless you actually feel good that it took you 10,000 miles to get hit by a car rather than 300. In the end, you got hit by a car, and the guy who infrequently cycles hasn't yet.


    Ah, the power of statistics. "People who switched to Progressive saved nearly $600."
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    Quote Originally Posted by Ryder321
    So, the more frequently a driver climbs into his racing car, the safer racing becomes?
    How do you get that, and what is its connection to the cycling statistics presented here?

    Relative mortality risk: It's measured in probability of dying per year, not per lifetime, don't ya know?
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    Quote Originally Posted by Kontact
    These studies tell us something we already know - people who do something frequently do it better than those who don't. But riding more doesn't make you "safer", unless you actually feel good that it took you 10,000 miles to get hit by a car rather than 300. In the end, you got hit by a car, and the guy who infrequently cycles hasn't yet.."
    No. That's not the right interpretation (or rather, that factor probably accounts for only a small part of the effect). The kilometers cycled is by the whole population, not the individual rider. What the stats suggest is that in places where there are more people on the road cycling, more of the time, each of them is safer (i.e., the chance of accident in a given number of kilometers is lower) than in places where fewer people cycle.

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    Quote Originally Posted by Kontact
    Well, what does the relative refer to?
    Relative mortality risk is kind of a standard concept. You adjust for age, sex, etc., and then compare the number of people in each group who die per year per 100,000 population. It's all described in detail here: http://archinte.ama-assn.org/cgi/con...ct/160/11/1621

    The figure means that if you take two people of the same age, same sex, same amount of leisure-time physical activity, same kind of work (desk job, physically active job, homemaker, etc.), same body-mass index, same smoking history (current heavy smoker, current occasional smoker, never smoked, used to smoke but quit), same blood pressure, and same blood lipid levels, you find that the one who cycles to work has a 30% smaller chance of dying in the coming year.

    The sample size was 13,375 women and 17,265 men, ranging in age from 20-93 years. They were studied for a period of 14.5 years, during which 2881 women and 5668 men died.
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    Quote Originally Posted by Kontact
    Ah, the power of statistics. "People who switched to Progressive saved nearly $600."
    Indeed.

    I find the creative application of language, "interpreting" the statistics, to be the most entertaining. Those weasels in marketing can perform breath-taking feats:

    "Government tests PROVE that no other aspirin is more effective than Bayer!"

    It's often hysterical!

    It's disturbing to find how often people think EXACTLY as those weasels in marketing intended them to think.

    Note: Government tests showed all aspirin brands to perform alike.

  11. #11
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    Quote Originally Posted by Fredke
    Andrew Gelman has a good blog post, referring to a more detailed article by Thomas Krag on cycling and safety:
    This is really fascinating.

    Andrew Gelman is a prize-winning statistician ("He has received the Outstanding Statistical Application award from the American Statistical Association, the award for best article published in the American Political Science Review, and the Council of Presidents of Statistical Societies award for outstanding contributions by a person under the age of 40.") who linked to Krag's article on his blog because he thinks it's an example of a really good presentation of statistical data.

    Gelman writes, "check out ... the relatively sophisticated discussion of statistical principles ... sophisticated to what one usually sees in the media, anyway. (I'm not sure if this is a reflection of higher standards of statistical literacy in the Netherlands vs [United States], or if that's reading too much into it.)"

    But lots of people here claim to be so much better at statistics than Gelman that they can see what nonsense Krag's analysis is without even having to do the hard work of carefully reading it. I am simply blown away by the collective brain power on display here
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    Quote Originally Posted by Fredke
    How do you get that, and what is its connection to the cycling statistics presented here?

    Relative mortality risk: It's measured in probability of dying per year, not per lifetime, don't ya know?

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    Quote Originally Posted by Fredke
    This is really fascinating. I am simply blown away by the collective brain power on display here
    You're a moderator?

    And this is how you talk to people?

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    Talking Y'all air ignert!

    Quote Originally Posted by Ryder321
    You're a moderator?

    And this is how you talk to people?
    Some uh y'all jes laike tew mouf off.

    Here's another one. Speed kills.

    I have always suspected, being a dedicated and enthusiastic rider, that bicycling is a life affirming activity, and therefore in the long haul, presents a lower risk of death. IMO it's also safer than driving, due to the considerably less speeds and lower impact intensities when crashing.

  15. #15
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    Nice post, Fredke.

    On the other side other coin, I'm reminded of the helmet debate, I think it was Australia, where studies showed that mandatory helmet laws actually increased overall risk because fewer people cycled.

    Anyway, more people on bikes is something I support.
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  16. #16
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    Quote Originally Posted by Ryder321
    You're a moderator?

    And this is how you talk to people?
    You think that is bad?

    You should see how I talk to people!



    BTW FWIW he is the moderator of a forum, not all forums. HTH ETC ALT
    Quote Originally Posted by the_dude
    these are better than i was expecting, and my expectations were already rather high.

  17. #17
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    This just plain sounds like to many people have to much time on their hands to me! Go ride your bike and stop worrying about dieing! It will happen eventually no matter what!
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    Quote Originally Posted by Fredke
    This is really fascinating.

    Andrew Gelman is a prize-winning statistician ("He has received the Outstanding Statistical Application award from the American Statistical Association, the award for best article published in the American Political Science Review, and the Council of Presidents of Statistical Societies award for outstanding contributions by a person under the age of 40.") who linked to Krag's article on his blog because he thinks it's an example of a really good presentation of statistical data.

    Gelman writes, "check out ... the relatively sophisticated discussion of statistical principles ... sophisticated to what one usually sees in the media, anyway. (I'm not sure if this is a reflection of higher standards of statistical literacy in the Netherlands vs [United States], or if that's reading too much into it.)"

    But lots of people here claim to be so much better at statistics than Gelman that they can see what nonsense Krag's analysis is without even having to do the hard work of carefully reading it. I am simply blown away by the collective brain power on display here
    I did not read the full article earlier, and having done so I retract what I said.

    However, using separate cultures to present safety and health statistics, then suggesting underlying causes definitely has its problems. Gun control proponents like to talk about the US, Japan and Yemen, where gun violence and gun ownership are correlated. And gun rights activists like to talk about Switzerland and Israel, where machineguns are plentiful and murder low, suggesting an inverse relationship.

    It would appear that the author has demonstrated that countries with bike cultures are safer for bikers - which is undoubtedly true. But the implied idea that increasing bike use will produce such a culture isn't entirely born out. It stands to reason, but see the above examples of reasoning. Having spent time with lots of Dane's, I'm not really shocked that they are less likely to run over cyclists than the French. And the French, knowing their own habits, are probably less likely to see cycling in the same light as the Dane's and start pedaling.

    So what can be done with this data, aside from selecting the Netherlands for your next cycling vacation?
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  19. #19
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    Quote Originally Posted by Fredke
    Andrew Gelman has a good blog post, referring to a more detailed article by Thomas Krag on cycling and safety:







    Bottom line: the more people cycle, the safer it is to cycle.


    And if you include the health benefits of cycling as well as the risk of accidents, here's what you find:

    Couldn't the data here also make the bottom line's contrary work; i.e., that the safer it is to cycle, the more people cycle?

  20. #20
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    Quote Originally Posted by Ryder321
    You're a moderator?

    And this is how you talk to people?
    That's why I moderate the Politics Only forum.
    Fredke commented in your thread. You won't believe what happens next!

  21. #21
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    It appears that at 1000-1200 km/year fatality risk drops to zero. Awesome.
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