|release date: 21st June 2004||number: PR126|
|Speed camera report is false
NEWS: For immediate release
The recent official report on the benefits of UK speed cameras is totally unjustified in its headline conclusions, says Safe Speed.
The largest problem arises from the naturally random distribution of road accidents, and the rule that requires cameras to be placed where there have been a high level of accidents over a fairly short period.
When a camera is placed where there has been a temporary upward blip in accident figures, we should not be surprised that the blip does not recur. Such placement appear to be extremely commonplace and the effect results in an illusion of benefit. Even genuine accident black spots are most likely to receive a camera after an especially bad spell.
Safe Speed has written to Professor Ben Heydecker, the report's apparent lead author, demanding his resignation and the withdrawal of the report.
Paul Smith, founder of the Safe Speed road
safety campaign, explains: "This error is well known to statisticians,
road safety professionals and the Department for Transport (DfT) as "regression
to the mean". In
Paul continues: "Last year's report contained the same error, and Professor Heydecker admitted as much on the BBC Radio 4 programme "more or less". It is all the more shameful then, that the error has been repeated in the new report."
Make no mistake. This is a huge error. In a well known study of 2,500 crossroads in Sweden, it was noted that those junctions left untreated showed an improvement in accidents of more than 50%. If a similar error exists at UK speed camera sites, and it might well, then the truth could be that speed cameras caused a 10% increase in killed and seriously injured accidents at speed camera sites.
"The problem with regression to the mean", explains Paul, "is that accidents may not be reducing at all. They simply take place somewhere else. That is exactly what seems to be happening especially to our fatal road accidents."
Notes for editors.
Letter to Professor Heydecker:
Regression to the mean primer:
Previous letters to Professor Heydecker
regarding last year's report:
Professor Heydecker and Regression to the
mean on Radio 4, 29th January 2004, full transcript and audio available:
DfT Report: "The national safety camera
programme: Three-year evaluation report":
DfT Road Safety Good Practice Guide:
* UK road deaths have not fallen since
1998. In Germany road deaths
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
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 22/06/2004. Last update 22/06/2004