Safe Speed Forums

Have a look here for the figures for the speed cameras in your area:
http://www.dft.gov.uk/stellent/grou...cst?n=10540&l=2

Interesting statistics, but can somebody explain something to me??

They show the anual average KSI figures for a given site for the 3 years prior to installing a camera. Now that would suggest they take the KSI figures for each year, add them up and divide by 3.

That being the case how can you have an anual average of "0.7" as this would equate to 2.1 people Killed or Seriously injured over 3 years, how can you have "0.1" of a person killed, or do they count an amputation as a partial kill

I am no statistician / mathematicain, but I get the feeling that they are using the wrong number of significant figures in the calculations in an effort to stop most things rounding down to 0.

Can you check the URL, please? It won't work for me.

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Keep right on to the end of the road ...

Try this then:
http://www.dft.gov.uk/stellent/groups/d ... =10540&l=2

I am sure Paul will have plenty to say about the figures.

To start with they are taking an average over 3 years and comparing it to one year. The average is taken over three years of their choice, i.e. the years they used to justify the camera in the first place. We know they abuse regression to the mean to make their figures look good.

What is really worrying is the number of sites showing a substantial rise! (though we really need to be comparing like with like to be fair).

The reports are also very light on detail. I would have liked to have seen average speed data for before and after (not just past the camera) and number of tickets issued.

And can anyone explain why it takes over six months to get these figures together?

So an increase in casualties at a camera site can actually mean the camera is still effective? Who came up with that and what planet are they from? But they have to try and make things sound better so they came up with a couple of excuses.So it's too early to tell and these are all excluded. So recently installed camera sites that do show a reduction should also be excluded on he same grounds. Bet they haven't done this though, as they'd have to reduce their claims about the numbers that are allegedly saving lives.It's just as wrong to assume that they may have been effective. Until the partnerships get their fingers out and provide the correct data these are an unknown, but the data that is there doesn't look so good. But that's also an unpleasnt admission so it's handy that there's an excuse for not counting them. Again, you have to wonder if this has been applied to cameras that have seen a reduction. Were they excluded from the beneficial figures? Doubt it.

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Make everything as simple as possible, but not simpler - Einstein

Nothing wrong with the calculation, if you check the spreadsheets the actual cell has the 'unrounded' figure (check London Sheet Pre, cells M25-27 for example).

As to the averages absolutely no problem, if two deaths were recorded in three years the average is 2/3 or 0.6 recurring or as you are taught at school this rounds up to 0.7 to one decimal place. If it was a scam then the 1/3 figures would be rounded up to 0.4 not down to 0.3.

BTW If they rounded to nearest significant figure the 2/3 would round up to 1 and the 1/3 down to 0. Rounding to decimal places is the correct method here.

A25 in Surrey, the village of Bletchingley - the GATSO there was painted yellow a few months back (i.e. welcomed into the netting-off club) and around about the same time a very short strech of the road - say a few tens of meters either side of the camera - got resurfaced. This is right outside a school sports ground and a pub car park.

Someone's life may be saved by this - but will we know which of the two things? We know which will get the credit, though, don't we

arthurdent

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DO NOT PANIC

A lot of the camera sites report a figure of 0.3 for the three years before, which equates to 1 casualty in three years. The 'after' figure is for a period of one year, so it's nonsense to assume that casualties have dropped just because this figure is 0. All it needs is just one casualty in the next two years. I suspect that in two years time most sites will have shown an increase.
There are also a lot of sites which show the same figures (mostly zeros) in both columns. This indicates no change, ie the cameras cannot be said to have reduced casualties, so they are ineffective.
Anyway, why don't they show the figures for the three years before the cameras were commissioned? That way we'd be able to compare, in most cases, the three years before to the three years after.

I wonder why they went to such great lengths to obfuscate the figures.

Regards
Peter

Sheesh, and they want more?



and brumstrom still thinks they save lives?

which could explain why he's calling for hidden ones... http://news.bbc.co.uk/1/hi/uk/3842187.stm

Not sure if it's already been posted, just catching up after being away a few days

Yes, some people (who have been caught speeding by a camera?) seize on anything, true or false, to confirm their prejudice. I'd like to know which camera sceptics have not been pinged? Come on, own up.

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I stole this .sig

Not me. Full, clean licence, and intend to keep it that way.

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Keep right on to the end of the road ...

Me too, no convictions for 23 years. I believe Paul Smith has had a clean licence for many years, too.

In reality, someone who takes an active interest in driving and safety issues is much less likely to get caught than your auntie doing 36 in a 30 that used to be a 40.

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

Somehow I missed this thread completely.

We cannot deduce ANYTHING (and I really mean ANYTHING) from the figures published because we know that there's a regression to the mean effect, but we don't know (and can't determine) how big it is. It could be bigger or smaller than the total benefit suggested by the raw figures.

See: http://www.safespeed.org.uk/rttm.html

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

The figures given are KSI/km, so when site length is ivided into the number of KSIs the figure for KSI/km will give you a decimal on occasion

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It's Champion Man

Well, A camera has appeared near my road junction as its an accident blackspot. Which I'm not in disagreement with. However, having lived here for about a year now, I've seen about two or three crashes. I'm assuming at least one fatality judging by the plastic remains of roses tioed to the railings. The thing is, these are caused by red light jumpers and not speeding. The juntion is fairly major, and as the main road is coming over a bridge, its hard to see the lights. Also, the cross road itself is also on a small hill, meaning when turning right (ie onto main road) its difficult to see who's coming. People tend to pull out when they assume people have stopped....

This is princess rd / mauldeth rd west in Manchester junciton by the way.

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uzz

How about this for the 'benefits' of cameras:

I paid a visit to the Strathclyde site www.camerascutcrashes.com to find the following on their home page:

New figures on how the Glasgow cameras have been saving lives were released by the Westminster Government in June 2004 covering the period March 2000 to April 2003.

They revealed that the number of people killed or seriously injured at camera sites FELL BY 34 PER CENT.

That's great news because it means our roads are becoming safer. Safer for children. Safer for our senior citizens. Safer for everyone.

Now that got me thinking, 'cos I was sure they had previously claimed a far better result so I did a search of their news archive and, sure enough http://www.camerascutcrashes.com/news_a ... successful about 3/4 of the way down the page:

11th February 2003
Strathclyde safety cameras most successful in Britain

Consultants commissioned by the Government found that nowhere across a range of UK areas was the scheme more successful in reducing deaths and injuries on the roads than in Glasgow during a two-year pilot between April 2000 and March 2002.

It found: PEOPLE killed or seriously injured FELL by 67 per cent at cameras locations

So, in Feb 03 the KSI reduction claimed for the period April 2000 to March 2002 was 67%. In June 04 they are claiming 34% reduction March 2000 to April 2003.

WTF?? Taking their own figures at face value and ignoring RTTM etc, they had a good first 2 years but lost 50% of the previous gains in the 3rd year. Hardly the resounding success they are claiming on the homepage. If they're going to be completely honest they should change the claim to:

That's bad news because it means our roads were becoming safer but are now becoming more dangerous again. More dangerous for children. More dangerous for our senior citizens. More dangerous for everyone.

Surely you all have points on your licences, if cameras are causing so many accidents that result in death that never did before!

Or are you saying that some drivers actually can stay within the limit - hence no points - and stay accident free?

Make up your minds, if cameras and keeping below an 'artificial' speed limit is the cause of a loss of trend surely all you motorists would be getting either caught speeding or involved in more accidents?

Your case seems illogical to me.

I don't necessarily stay within the limit - I tend to drive at speeds which I consider to be appropriate, and always have. But I've never been pinged, and have also not had an accident for going on 30 years.

Regards
Peter