|release date: 15th July 2004||number: PR131|
PR131: Continuing fraudulent speed camera claims
Information for editors and journalists - NOT a press release for publication
Almost all the claims we hear for speed camera benefits in terms of reduced casualties, accidents, serious accidents, "KSI" or fatalities are FRADULENT and prepared on a FALSE basis.
The Department for Transport says, in "The Road Safety Good Practice Guide":
"5.119 This effect, sometimes called bias by selection, complicates evaluations at sites with high accident numbers (blackspot sites) in that these sites have often been chosen following a year with particularly high numbers occurring. In practice their accidents will tend to reduce in the next year even if no treatment is applied. Even if three-year accident totals are considered at the worst accident sites in an area, it is likely that the accident frequencies were at the high end of the naturally occurring random fluctuations, and in subsequent years these sites will experience lower numbers. This is known as regression-to-the-mean."
The error is very well understood in road safety circles and it is undoubtedly fraudulent to create figures for speed camera benefits without accounting for this statistical effect.
With the rules for speed camera placement in partnership areas we estimate the size of the benefit illusion "at speed camera sites" to be 50%. So when a 40% benefit is claimed we might apply compensation for regression to the mea effect and conclude that the real effect of the cameras was to RAISE accidents by 10%.
Before publishing wild and inaccurate claims for speed camera effectiveness I urge you to ask:
"How have these figures been corrected for the regression to the mean effect?"You don't have to take my word for it - ask a statistician.
Please don't contribute to misleading the public.
If you require any further information, please don't hesitate to get in touch.
Notes and links
Comments regarding the recent DfT report
on the Numberwatch web site:
Recent Safe Speed letter to Professor Heydecker:
Professor Heydecker admits the error on
DfT Report: "The national safety camera
programme: Three-year evaluation report":
DfT Road Safety Good Practice Guide:
Professor John Adams (UCL) quoted in The
Times, 25th June 2004
Professor Mervyn Stone (UCL) See...
About Safe Speed:
Since setting up Safe Speed in 2001, Paul Smith, 49, an advanced motorist and road safety enthusiast, and a professional engineer of 25 years UK experience, has carried out about 5,000 hours of research into the overall effects of speed camera policy on UK road safety. We believe that this is more work in more detail than anything carried out by any other organisation. Paul's surprising conclusion is that overall speed cameras make our roads more dangerous. Paul has identified and reported a number of major flaws and false assumptions in the claims made for speed cameras, and the whole "speed kills" system of road safety.
The inescapable conclusion is that we should urgently return to the excellent road safety policies that gave us in the UK the safest roads in the World in the first place.
Safe Speed does not campaign against speed
limits or appropriate enforcement of motoring laws, but argues vigorously
that automated speed enforcement is neither safe nor appropriate.
Contact Safe Speed:
We are available for press and media interviews.
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Created 18/07/2004. Last update 18/07/2004