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Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
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 Posted: Tue Nov 09, 2010 2:28 am Post subject: |
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| M8TJT wrote: | The survey must be carried out at the time of day when the traffic is light enough to give people the choice as to whether to speed or not for the survey to have any meaning. I rest my case (for the time being)  |
It is a fair point too.  I'm just a bit jumpy because of all the dodgy statistics bandied about.
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MaFt
Pocket GPS Staff
Joined: Aug 31, 2005
Posts: 15137
Location: Bradford, West Yorkshire
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| Posted: Tue Nov 09, 2010 3:46 pm Post subject: |
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| M8TJT wrote: | | The survey must be carried out at the time of day when the traffic is light enough to give people the choice as to whether to speed or not for the survey to have any meaning. I rest my case (for the time being) |
but even then, the survey is biased towards times when people are able to speed. which we all know is not 24 hours a day yet these results would then imply that XX% of road users speed when, in reality, it would show that at certain times of the day XX% of people speed.
statistics can be a real pig 
MaFt |
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M8TJT
The Other Tired Old Man
Joined: Apr 04, 2006
Posts: 10118
Location: Bexhill, South Sussex, UK
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| Posted: Tue Nov 09, 2010 4:17 pm Post subject: |
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So those statistics would show the best time to dust down your LTI 20.20 and go and book a few speeders 
And you can't get a statistical increase in speeding at the time of day that it is not possible to speed. So that statistic would prove absolutely zilch. So you MUST pick the right time to gather the data. And of course, the 'before' data must have been taken over the same period and the same time |
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DennisN
Tired Old Man
Joined: Feb 27, 2006
Posts: 14892
Location: Keynsham
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| Posted: Tue Nov 09, 2010 7:40 pm Post subject: |
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| MaFt wrote: | | but even then, the survey is biased towards times when people are able to speed. which we all know is not 24 hours a day yet these results would then imply that XX% of road users speed when, in reality, it would show that at certain times of the day XX% of people speed. |
BUT it should first of all say that XX% of people drive at XX% of the time. So by the time you get down to XX% of the XX% people of the XX% time, you then take away the number you first thought of and the answer is 47 (which, expressed as a percentage of 12,673, is about 0.37%).
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Dennis
If it tastes good - it's fattening.
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aj2052
Frequent Visitor
Joined: Jul 03, 2005
Posts: 1431
Location: Leics,UK
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| Posted: Tue Nov 09, 2010 8:16 pm Post subject: |
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I make it 0.XX%
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M8TJT
The Other Tired Old Man
Joined: Apr 04, 2006
Posts: 10118
Location: Bexhill, South Sussex, UK
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| Posted: Tue Nov 09, 2010 8:18 pm Post subject: |
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| DennisN wrote: | | the answer is 47 (which, expressed as a percentage of 12,673, is about 0.37%). |
Good grief Dennis, you appear to have got your XXs mixed with your YYs, because as all HHGTTG fans know, the answer is always 42  Now what was the question again  |
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PhilAsh
Occasional Visitor
Joined: Nov 18, 2007
Posts: 9
Location: Nottingham
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| Posted: Tue Nov 16, 2010 4:01 pm Post subject: Re: Oxfordshire fixed speed cameras to be switched back on! |
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| DennisN wrote: | | Skippy wrote: | | If they were really interested in a scientific measurement then they would have placed a large number of car counters (the rubber strips across the road) which count the number of cars and record their speed before and after the announcement so they could make a scientific assessment of the actual change in behaviour. |
My bold/colour. Do those rubber things actually record speed? - I always thought they only counted and not entirely accurately at that. |
DennisN,
There are two different uses of the rubber strips. One is to provide survey information. In this case, the strips are connected to a grey box at the side of the road. (Often chained to a streetlamp).
The other is for enforcement. The police usually place these out, and then hide around the corner. Someone is concealed viewing the strips and on the radio to the colleagues around the corner.
I was caught speeding using this method some 20 years ago now, but the technology is still valid.
I think they add a third strip sometimes as a countercheck and I think they just record the details rather than stopping you around the corner.
I also think they are only really used on slower roads as they rubber strips can be ripped out at high speeds/torque loads.
To be safe, if I see these, I slow down.
Phil. |
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