UK and Europe · Public discussion

local ABD letter

Started by David Martin · · Last activity · 5 posts · 739 views

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UK and Europe
Published
6 April 2004
Last activity
7 April 2004
Original author
David Martin
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5
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  1. This was in the letters page of today's Courier..

    ----

    Sir,‹The letter from David Phillips (April 2) says in
    relation to the current speed camera debate that the police
    do not make the laws and are only doing their job.

    However, what the police and Tayside Speed Camera
    Partnership are not entitled to do is, by the creative use
    of statistics, present their road safety record as a roaring
    success when the reality is that it is an abysmal failure.

    The fact is that for the last two years, road deaths in
    Tayside have increased substantially year on year, but the
    police and the Speed Camera Partnership are deliberately
    attempting to conceal this from the public.

    I wasn¹t aware deceiving the public was part of a police job
    description. Eamon Scott, Tayside Co-ordinator, The
    Association of British Drivers. Main Road, Hillside.
    ----
    So, being the scientist I am I went looking for the figures.

    Two years ago the total number of deaths on scottish roads
    was the lowest ever (since 1950's when records began). So I
    wrote a quick reply..

    ---

    Sir,

    Eamon Scott (letters, 6th April) derides the chief police
    officer for a 'creative use of statistics' yet himself
    indulges in the same practice.

    Casualty rates vary from year to year so some years they
    will be higher and some years lower. Two years ago the
    figures for all of Scotland were the lowest on record. It is
    hardly surprising then that this years figures are slightly
    higher. The trend over the last five years is definitely
    downwards despite this recent blip. Quoting just two years
    as a trend is hardly an honest approach.

    Excessive speed is a contributory factor in over a third of
    accidents, and speed is directly related to the severity of
    accidents. Curbing speed is a key measure that can be done
    through automated means, freeing up police resources to
    police the roads in a more effective manner.

    Accidents in the vicinity of speed cameras drop dramatically
    but these only cover a tiny fraction of the road network.
    What we need are more cameras, not less so that speeding is
    placed in it's proper context, on the race track, rather
    than on the street endangering other road users.

    Motorists who do not know the speed limit or who fail to
    observe it though incompetence or deliberate choice have
    only themselves to blame for the eventual fines. If it is a
    stealth tax then it is the only one that is voluntary.

    Yours Sincerely

    Dr David Martin

    ----

    I doubt it will be published but it at least adds fuel
    to the fire.

    ..d

  2. On 6/4/04 1:39 pm, in article [email hidden],

    David Martin said:


    I doubt it will be published but it at least adds fuel to
    the fire.

    OK, The local rag published in full, even giving it the top
    of the letters prime billing with the headline 'More cameras
    needed to put speed in its place'
    (thecourier.co.ukletters.asp)

    ..d

  3. re: statistics

    If you are a statistician, then you will no doubt realise
    that the statistics used (on both sides of the argument) is
    generally a load of cr*p. The line the Speed Camera
    Partnerships tend to use is along the lines of;

    "We placed cameras in accident blackspots, and compared
    to the 3 years before, we found that accidents had
    dropped by x%".

    Whilst there are going to be genuine accident blackspots,
    there may be some places where it's just been rather unlucky
    that there have been a few accidents in that area.

    The government guidelines are that there must have been 4
    KSI (killed or seriously injured) accidents in the last 3
    years for a place to be an Accident Blackspot and hence that
    a GATSO camera can be put up. Lets assume that a site has an
    intrinsic accident rate of 0.5 KSI accidents per year on a
    stretch of road. Using the poisson distribution, we get that
    in a 3 year period P(KSI < 4) = 0.9344 - this means that the
    chance that this site becomes an accident blackspot for any
    given 3 year period is about 0.06564 -
    i.e. just over 14:1 against. So, it's quite unlikely that
    it'll become an accident blackspot in any normal 3 year
    period, but if you measure it for a few years, you are
    relatively likely to see it hit 4 accidents in 3 years
    in at least 1 of them. Let's say that in one 3 year
    period, we measured 4 accidents, and then a camera got
    put up. In the following 3 years, the probability of
    accidents falling at the site is over 93%, even if the
    camera doesn't change the intrinsic accident rate at
    all for the site!

    Let's say that we have a site where the intrinsic accident
    rate is 1 per year, and some road improvement is carried out
    after 6 accidents were recorded in 3 years (1:11 chance of
    at least 6 accidents happening in 3 yrs). What if, after the
    road "improvement" was finished, the intrinsic accident rate
    rose to 1.1 per year. Would this get noticed at all?

    The probability of less than 6 accidents occuring with the
    new rate is 88% - so the road is intrinsically more
    dangerous, but the accident rate has fallen!!!

    Remember, there are lies, damned lies, and statistics.

    Richard

  4. Quoted message said:

    OK, The local rag published in full, even giving it the
    top of the letters prime billing with the headline 'More
    cameras needed to put speed in its

    Excellent, well done TerryJ

  5. On 7/4/04 7:39 pm, in article
    [email hidden], "Terry"

    Quoted message said:
    Quoted message said:

    OK, The local rag published in full, even giving it the
    top of the letters prime billing with the headline 'More
    cameras needed to put speed in its

    Excellent, well done TerryJ

    I got some positive feedback from friends (general public,
    not cyclists) who had seen it, including one police officer.

    ..d

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