• On the increase in cyclist numbers

    From Spike@aero.spike@mail.com to uk.rec.cycling on Fri Sep 19 13:39:28 2025
    From Newsgroup: uk.rec.cycling


    In an article concerning the death of a cyclist following a collision with
    a moped, the following significant incident was mentioned in the report
    linked here:

    <https://road.cc/content/news/cyclist-killed-racing-moped-rider-bike-lane-315977>

    Quote:

    Citing Transport for London (TfL) data, the Telegraph claimed that from
    January to August 2022, three people were seriously injured while riding
    bikes on the segregated cycleway [rCyCycleway 9rCO] rCo two in collisions involving motor vehicles at junctions, and one in a crash involving three bikes.

    Unquote

    A three-cycle collision is surely a great rarity, but it is a mathematical certainty that as the number of cyclists increases, so is the probability
    of these extremely rare events becoming more likely.

    With an exponential increase, the number of potential collisions grows significantly as more cyclists are added. For example, if you have n
    cyclists, the number of potential pairwise collisions can be calculated
    using the formula n(nreA1)/2.

    For n>>1 this reduces to n^2/2, so for a ten-fold increase in cyclist
    numbers, there will be 50 times as many two-cycle collisions.

    For three-body collisions, the increase is given by
    n(nreA1)(n-2)/6. For a ten-fold increase in the number of cyclists, where
    1 the rate of collisions will be given by 1000/6 =167 times. A rate of 1 such collision every ten years becomes 1 every three weeks.

    These are dismal numbers, since some of the collisions will result in fatalities. The much-lauded rCyVision ZerorCO simply cannot be met by replacing motor vehicles by cycles.
    --
    Spike

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  • From Spike@aero.spike@mail.com to uk.rec.cycling on Fri Sep 19 13:46:12 2025
    From Newsgroup: uk.rec.cycling

    Spike <aero.spike@mail.com> wrote:

    For three-body collisions, the increase is given by
    n(nreA1)(n-2)/6. For a ten-fold increase in the number of cyclists, where
    1 the rate of collisions will be given by 1000/6 =167 times. A rate of 1
    such collision every ten years becomes 1 every three weeks.

    That should have rendered as follows:

    For three-body collisions, the increase is given by n(nreA1)(n-2)/6. For a ten-fold increase in the number of cyclists, the rate of collisions will be given by 1000/6 =167 times. A rate of 1 such collision every ten years
    becomes 1 every three weeks.
    --
    Spike

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