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THE EMERGING TRUTH OF INEFFECTIVE SPEED CAMERAS
In the report of the 4th year of the speed camera hypothecation scheme, published today by the Department for Transport (DfT) we finally get an estimate for THE major error in speed camera claims.
The error is a statistical effect called 'regression to the mean' (RTM or RTTM). Appendix H contains:
"Thus RTM accounts for about three fifths of the observed reduction in FSCs (Fatal and serious collisions) with the effects of the cameras and trend each accounting for a fifth."
This is a clear and unequivocal admission that the benefits of speed cameras have been wildly exaggerated.
Last year's claim of 42% reduction in killed and seriously injured at speed camera sites becomes 10.5%.
As the truth about speed camera ineffectiveness finally emerges it is amassing that the DfT has not got the balls to pull the plug on the whole project.
Speed cameras make our roads far more dangerous by focussing everyone onto the wrong safety factor.
They need to be scrapped immediately before more people die of 'bad policy'.
FACE FACTS, MR DARLING AND YOUR DEPARTMENT ARE ABYSMAL, YOU SHOULD RESIGN.
The DfT move away from speed cameras is a shameful and cowardly attempt to pretend that their policy has been working.
In truth speed camera policy has been grossly overestimated and misunderstood by an increasingly incompetent DfT.
That truth emerged buried deep in the last pages of the 4th year report of the speed camera funding scheme.
The report admits that gross statistical errors have overestimated the benefits of speed cameras by up to a factor of five. (This is mainly the RTTM error, see notes for editors below, and appendix H of the new report)
Realising their gross error, the DfT now seems to be trying to move quietly away from speed cameras and the disastrous speed camera funding scheme.
Confidence must be restored in official road safety messages and while they; the DfT, pretend that nothing is wrong it quite simply is not going to happen.
Mr Darling should admit he is wrong, pull the plug and resign. His policies are responsible for thousands of road deaths which proper policies could have prevented."
The report is a fraud of both media and public The "4th year" report is worded in such a way to have widely misled media and public regarding the true effect of speed cameras.
The important headline figure of '42% reduction in killed and seriously injured' contains a gross statistical bias that has already been very widely quoted as if it were the true benefit of speed camera operation.
This statistical bias is called 'regression to the mean' (RTTM or RTM) and has a large effect.
Amazingly, although the report attempts to suggest that RTTM cannot be accurately estimated on available data, it actually uses two similar estimates! (Table 4.9 and appendix H)
According to table 4.9:
0.36 RTTM + 0.11 benefit = 0.47 total. Applying this to the
42% headline conclusion suggests:
42% reduction in KSI at speed camera sites is comprised of:
32% RTTM benefit illusion and 10% camera benefit.
According to appendix H:
* three fifths RTTM
* one fifth trend
* one fifth benefit
As the trend has already been calculated in the 42% headline figure, this becomes:
* three quarters RTTM
* one quarter benefit
This would therefore suggest:
42% reduction in KSI at speed camera sites is comprised of:
31.5% RTTM benefit illusion and 10.5% camera benefit
[ Ed: On top of this we have the safety squad banging on about the intolerably high road death toll but hardly anyone says a thing about the annual toll of deaths from hospital acquired infections which runs many times higher!
Rather typical of an inept and incompetent government that is corrupt, lies incessantly, has a traitor for a Prime Minister and wants to pay itself an extra 22% and says it is OK to dine convicted paedophiles in the House of Commons]
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