M4 Speed Camera results

[k50 del]

The Wiltshire Scamera partnership have just been on the BBC claiming the speed cameras on the M4 are a success as they've reduced accidents by 57%

In true BBC style, no data was given on the time frame involved, or how many accidents were actually caused by speed.

Anyone (Paul Smith??) have access to the actual figures and dates?

[autismuk]

There's something on the ABD site www.abd.org.uk/pr/483.htm

The figures seem implausible ; undoubtedly it is data selection.

[turbobloke]

Yes, the ABD PR is being aired widely at the mo.
Paul's first PR on this lists the truth behind the spin:

"ISSUE 1: There's no good reason to expect speed cameras to reduce M4 crashes.
Figures obtained by the Association Of British Drivers for M4 crashes revealed that 15% had 'excessive speed' as a contributory factor. Many 'excessive speed' crashes do not involve exceeding a speed limit. So even a 'perfect' change in driver behaviour caused by the cameras should not be expected to reduce crashes by more than 15%.

ISSUE 2: Selection bias / regression to mean effect
It is a fact that we tend to apply road safety treatments to places where there have recently been high casualty numbers. This leads to a selection bias effect because some of those high casualty numbers will be due to nothing more than random chance. With no treatment applied, abnormally high casualties tend to reduce anyway. This effect is also known as 'regression to the mean' (RTTM), and is very well understood in road safety circles. Recent DfT figures suggest that RTTM accounts for three quarters of the benefit that has previously been claimed for speed cameras.

ISSUE 3: Too soon to tell
Road crash figures are subject to considerable random variation. It is
unprofessional and illegitimate to make claims based on a single year's
figures. Examples of random variation appear strongly in the figures released by Wiltshire Camera Partnership. e.g. between 2003 and 2004 personal injury collision reduced by 37% from 261 to 165. There were no cameras on the M4 at the time.

ISSUE 4: Cherry picking of comparison groups.
By choosing favourable years or casualty groups the changes can be exaggerated to show a desired effect. Other figures - for example M4 casualty figures for Wiltshire in 2000 and 2001 - are unpublished. Even within the published figures there is ample room to spin the story. For example we could say: between 2001 and 2002 fatal and serious casualties increased from 18 to 31 - an increase of
72%. This is just as valid as some other comparisons that are being made.

ISSUE 5: System trends
During the period in question we have tended to see national reductions in injury and serious injury collisions. So if the M4 in Wiltshire was typical of UK roads we would have expected to see the numbers come down anyway,
irrespective of any local treatment. This has not been allowed for and clearly exaggerates the benefit being assigned to the cameras.

ISSUE 6: Local conditions
Changes in local conditions have a marked effect on accident rates. For example, large long term motorway road works would be expected to lead to a reduction in casualties.

ISSUE 7: Re-routing
Traffic chooses a different route because of the cameras and have their crash elsewhere. And in the case of the M4, the common alternative is M3/A303. Some of the apparent reduction may be due to traffic choosing a different route to stay away from the M4 cameras.

These 7 issues tend to exaggerate the benefits claimed for M4 speed cameras."

His second one, just in the mailbox, says that the Wilts top scamp has admitted in a radio interview there's no evidence the drop was caused by their vans. No doubt Paul will be saying more on this...

[7db]

I should have thought causality would be the peg to hang a counter-argument on.

I hung a small piece of string (passim) on the bridge at Junction 17. This caused a 400% reduction in casualties on the M4. Any net (positive) difference must be due to the SCP's vans.

[puggit]

Lets not forget the almost daily tales of woe when the talivans first appeared. There were frequent serious accidents on the Wiltshire stretch.

[turbobloke]

7db said:

I should have thought causality would be the peg to hang a counter-argument on. I hung a small piece of string (passim) on the bridge at Junction 17. This caused a 400% reduction in casualties on the M4. Any net (positive) difference must be due to the SCP's vans.

A long, long time ago I suggested placing hidden ABD Safety Gnomes at hotspots to prove that, in fact, gnomes are the future for road safety. It was seen as potentially in poor taste but it's had its supporters and would seem more likey to work, after all gnomes are powerful

[safespeed]

turbobloke said:

His second one, just in the mailbox, says that the Wilts top scamp has admitted in a radio interview there's no evidence the drop was caused by their vans. No doubt Paul will be saying more on this...

Yes! It was a fun outing on BBC radio Swindon for Dave Frampton (partnership manager) and I. The second PR, issued at 9:15 this morning is as follows:

PR303: Wiltshire Partnership admits: 'no evidence'

news: for immediate release

Following figures released by Wiltshire camera partnership claiming success for
their cameras on the M4, Dave Frampton, (Partnership manager) speaking on BBC
Radio Swindon this morning admitted that there was NO EVIDENCE WHATSOEVER to
suggest that their camera vans had caused a reduction in crashes on the M4.

Paul Smith, founder of the Safe Speed road safety campaign
(www.safespeed.org.uk) said: "This is typical of the cowboy behaviour of camera
partnerships. They claim success at every opportunity based on no sound
evidence whatsoever. Every lie or exaggeration distorts road safety priorities
and risks increasing danger on our roads."

"After nearly 14 years of speed cameras on UK roads, there is precious little
evidence of any benefit, despite £800,000,000 in fines issued to around 13
million motorists. Road deaths are NOT falling as expected and we're now the
slowest improving country in Europe."

<ends>

[puggit]

Paul, you might want to contact 2-ten fm radio (based out of Reading). Their lead story this morning is concerning the Wiltshire results and that Thames Valley 'Safer' Road Partnership (inc soundbite) are looking at these results and considering rolling the vans out in Berkshire

The M4 in Berkshire is incredibly busy and I would guess that the accidents here due to speeding are even lower then in Wiltshire.

[safespeed]

puggit said:

Paul, you might want to contact 2-ten fm radio (based out of Reading). Their lead story this morning is concerning the Wiltshire results and that Thames Valley 'Safer' Road Partnership (inc soundbite) are looking at these results and considering rolling the vans out in Berkshire The M4 in Berkshire is incredibly busy and I would guess that the accidents here due to speeding are even lower then in Wiltshire.

I've already pre-recorded an interview with them.

[puggit]

safespeed said:

puggit said: Paul, you might want to contact 2-ten fm radio (based out of Reading). Their lead story this morning is concerning the Wiltshire results and that Thames Valley 'Safer' Road Partnership (inc soundbite) are looking at these results and considering rolling the vans out in Berkshire The M4 in Berkshire is incredibly busy and I would guess that the accidents here due to speeding are even lower then in Wiltshire. I've already pre-recorded an interview with them.

Any ideas when it will be broadcast?

[turbobloke]

Between SafeSpeed and the ABD, most local and regional radio stations will be covered I'd guess. I believe there's also a TV news item being shot on a bridge over the M4, for Central TV, involving MMC of ABD and PH.

[dogwatch]

Any chance of a few spinmeisters being shot on the bridge as well?

[safespeed]

puggit said:

safespeed said: puggit said: Paul, you might want to contact 2-ten fm radio (based out of Reading). Their lead story this morning is concerning the Wiltshire results and that Thames Valley 'Safer' Road Partnership (inc soundbite) are looking at these results and considering rolling the vans out in Berkshire The M4 in Berkshire is incredibly busy and I would guess that the accidents here due to speeding are even lower then in Wiltshire. I've already pre-recorded an interview with them. Any ideas when it will be broadcast?

Sorry - no idea.

[puggit]

2-ten FM quoted Andy Cunningham from the 'British Association of Drivers' on the 11am news. Their story has turned around 100% to the fact that the cameras aren't working

[steve z]

See Wiltshire SCPs basis for their claims here:-

www.safetycameraswiltshire.co.uk/oneyear.doc

As has been mentioned, eventhough it is undeniable that KSIs have been reduced on that stretch of the M4 to claim that is purely down to cameras reducing speed is ridiculous and misleading to the public.

[deeps]

steve z said:

See Wiltshire SCPs basis for their claims here:- www.safetycameraswiltshire.co.uk/oneyear.doc As has been mentioned, eventhough it is undeniable that KSIs have been reduced on that stretch of the M4 to claim that is purely down to cameras reducing speed is ridiculous and misleading to the public.

Thanks for the link.

Why do they leave out 11th and 12th of April every year?

In 2004, there were 4 fatal collisions but only 3 fatalities. How does that work, I must be missing something very simple?

[deeps]

turbobloke said:

Between SafeSpeed and the ABD, most local and regional radio stations will be covered I'd guess. I believe there's also a TV news item being shot on a bridge over the M4, for Central TV, involving MMC of ABD and PH.

Just watched that on the local BBC. The coverage mainly went to the SCP boss and a traf pol, who both basically said if traffic is moving slower , collisions when they occur will be less serious.

[apache]

deeps said:

turbobloke said: Between SafeSpeed and the ABD, most local and regional radio stations will be covered I'd guess. I believe there's also a TV news item being shot on a bridge over the M4, for Central TV, involving MMC of ABD and PH. Just watched that on the local BBC. The coverage mainly went to the SCP boss and a traf pol, who both basically said if traffic is moving slower , collisions when they occur will be less serious.

oh give that bloke a medal, I guess he's an expert then. If traffic stops there will be no collisions at all, have their tiny minds reached that conclusion yet? Hows about working on ways to STOP COLLISIONS then, oh too expensive isn't it

[turbobloke]

deeps said:

turbobloke said: Between SafeSpeed and the ABD, most local and regional radio stations will be covered I'd guess. I believe there's also a TV news item being shot on a bridge over the M4, for Central TV, involving MMC of ABD and PH. Just watched that on the local BBC. The coverage mainly went to the SCP boss and a traf pol, who both basically said if traffic is moving slower , collisions when they occur will be less serious.

Yes, the BBC, that figures.