Road Safety News
 

20mph can reduce collisions – but compliance is challenging

Tuesday 9th December 2014

A new report says that while there is clear evidence that “reducing vehicle speeds results in fewer and less severe collisions”, getting drivers to comply with signed only 20mph limits is challenging.

The desktop research, carried out by the consultants Steer Davies Gleave for the London Borough of Merton and the London Environment Directors’ Network (LEDNet), was commissioned to “inform future 20mph policy in London”.

The report says that historically 20mph zones have been successful at reducing speeds by using physical traffic calming measures. However, at present limited resources and relaxed regulations mean that signed-only 20mph limits are now preferred, but “these tend to achieve smaller decreases in vehicle speeds”.

The challenge, it says, is to find ways to achieve reductions in vehicle speeds in signed-only 20mph limits, “so that safety benefits are still achieved”.

The report says enforcement is a “partial solution”, but describes “changed driver attitudes so that 20mph is seen as the appropriate speed in urban areas” as “the key to achieving sustained reductions in vehicle speeds”.

While acknowledging this will take time, is says “there are precedents such as attitudes towards drink driving”. It also highlights a potential role for new technologies such as Intelligent Speed Adaptation.

The report says at present publicity and marketing are seen as “ancillary measures rather than a core part of 20mph schemes”. Going forward, it says “supporting measures that foster cultural change need to be an integral part of all 20mph schemes”.

On vehicle speeds and collisions, it says that these are generally monitored over a relatively short period, but a longer period would provide more robust information.

On enforcement, it says that while police are becoming more willing to enforce 20mph, their position remains that “there should be no expectation for additional police resources”.

It adds that the evidence on vehicle emissions is mixed, with the effect dependent on fuel type and driving styles, and any impact on traffic noise is likely to be “negligible”.

The report also says there is some evidence that 20mph zones can reduce traffic volumes and increase the use of sustainable modes, such as walking and cycling, especially where 20mph is implemented as part of a wider package of measures.

Responding to the report, Rod King MBE, founder of 20’s Plenty for Us, said: “Explaining the benefits to drivers is key to lasting cultural change where 20mph makes places better places to be.”

NOTE TO CONTRIBUTORS
News stories about 20mph limits tend to produce lengthy discussion threads, but often these comprise multiple posts by a small number of contributors. To counter this, we are encouraging contributors to state their views once and then allow others to do the same - and then let the readers make up their own minds about the story. We welcome open debate and views from all quarters, but would like to avoid discussion threads, particularly on 20mph stories, becoming a dialogue between a small number of contributors - which can become repetitive and a little tedious for other readers. Thanks for your co-operation on this point.
Nick Rawlings, editor, Road Safety News

 

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Point taken Nick.

Well that's one new year resolution sorted! Seasonal greetings to you all.
Rod King, 20's Plenty for Us

Agree (2) | Disagree (2)
0

Just to answer a couple of points, there was a news item recently about the money around courses:
http://www.dailymail.co.uk/news/article-2863893/Ex-police-questioned-1-9million-paid-motorists-speed-awareness-courses-Crime-watchdogs-order-firms-open-books-investigate-murky-deal-struck-forces.html

We have essentially multi- £million industries in every county, and little apparent transparency and accountability to the public.

When I am in pedestrian or residential areas I am focussing on what is going on and not my speedo, and that often results in speeds far below 20 and probably sometimes above. I do not need to be treated like an idiot! We need to do much better with the limited resources we have.
Dave, Guildford

Agree (6) | Disagree (3)
+3

Sorry Nick but as Rod has misquoted me I feel it necessary to draw attention to it. I'm sure it's just a slip of the keyboard but I actually said "mis-sold as a universal panacea", that's to say encouraging people to believe they will make things better everywhere when they won't. I'll shut up now....
Tim Philpot, Wolverhampton

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+4

Well Dave, effective casualty reduction has been achieved by compelling traffic to moderate speed in selected areas, so I think the principle of making people observe a 20 limit or something close is established. But I can reference two schemes in Wolverhampton, one where we created a Home Zone and left the speed limit at 30 and one another nearby where we traffic calmed and introduced a 20 limit. They were both similarly highly effective at reducing casualties, so I have to question whether the change of speed limit helped. Speed limit reduction is not the goal in my mind, speed reduction is.

I don't know what your conception is of the financial motivations for speed limit enforcement so it's difficult to comment. But I'm aware many people (some otherwise quite sensible) think profit from speed enforcement goes to fund the bar at the Police Christmas party or something equally unacceptable. The truth is that different funding regimes have been tried particularly for camera enforcement but all have some controversial aspect. The current one involves revenue from speed awareness courses going to fund Police operation of speed enforcement and in many cases this is a loss-maker, at best a break-even as are a lot of enforcement regimes. Interestingly, the Government who stated they didn't wish to profit from the motorist still collect speeding fine revenues and vat on Speed Awareness. But before you think this might be funding the bar at the Home Office Christmas party I'd be inclined to suggest it gets recycled into the general public finances and pays for something more appropriate.
Tim Philpot, Wolverhampton

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+2

Rod:
My plea for restraint appears to be falling on deaf ears - that's six posts from you now in this thread!

My advice, as previously stated, is for contributors to make their point and not feel the need to respond to every single counter post, but rather to let readers make up their own minds about the merits of the various posts and points made.
Nick Rawlings, editor, Road Safety News

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+5

Dave
Could you explain how setting a speed limit of 20mph "evidences" an obsession with speed. And it would be useful if you could provide any evidence of the enforcement of 20mph limits being "out of control".
Rod King, 20's Plenty for Us

Agree (2) | Disagree (4)
-2

Tim
I not sure that anyone is "selling 20mph limits as a panacea". Certainly 20's Plenty for Us see it as a necessary foundation for providing an equitable street environment for communities, and many other things are complementary to this. The report also makes the case for developing a consensus around maximum speeds in residential and urban environments and we also see that as a crucial aspect. Indeed we feel that a discussion of the maximum speed on such streets acts as a catalyst for a valuation of the benefits of those streets as places for "people" rather than just "people in cars". And it would appear that "the people in cars" also see the benefits and it is good to see road safety campaigners working to optimise how that consensus change can result in behaviour change.
Rod King, 20's Plenty for Us

Agree (2) | Disagree (5)
-3

Tim:
Interesting points, from my point of view, being an engineer, I like to gather all of the objectives and factors and consider them together to produce a best overall compromise, and most decisions do involve some compromise. I have nothing against limits and enforcements as long as they are proportionate and based on a proper and unbiased consideration of all the factors against the objectives. But the very fact that we have some maximum speed limits of 20 is evidence in itself that some have simply become obsessed with speed alone and have lost sight of the other numerous factors. And as far as enforcement is concerned, it seems that the financial motivations are completely out of control. This is not a good overall situation likely to result in the best compromises.
Dave, Guildford

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+3

Terry's honest comment below is a clear illustration that contrary to Duncan's first comment, it is in fact very difficult to change the input in these situations. Studies have evidenced that many people attach more value to benefits that are immediate and personal, whether real or perceived, than to distant epemeral benefits. We can only really have a "system" which operates to maximum capacity without injury when people cease to be fallible and selfish, until then trying to induce margin for error is what matters.

I'm relieved at the relative objectivity of this work. I have no problem with the democratic process enabling people to vote for 20mph limts in their areas but I do not wish to see it mis-sold as a universal panacea because it is manifestly not.

It's interesting that those who oppose the removal of one arbitrary "number on a pole" in favour of another are not questioning the original number, although surely the same arguments would apply? I have often thought that the subtext of many contributors to this forum was that there should be no speed limits at all because they see no proof that speed causes collisions and because anything that distracts from the task of driving must necessarily increase collision likelihood. But to date I have not heard anyone openly campaign on this ticket. I wonder why?
Tim Philpot, Wolverhampton

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0

"The slower the initial speed relative to the road and traffic conditions, the less likely to need to panic stop". Indeed, and the road and traffic conditions are best determined by an intelligent interpretation of what is going on, something that the vast majority of drivers are pretty good at doing. And those that are not are unlikely to be influenced much by a number in a circle, particularly when that number is far below the normal, natural speed for typical conditions.
Dave, Guildford

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+4

20mph, what is the first picture that comes to mind? Busy high street at 3:30pm as children come out of school or 3:30am with nobody in sight because 99per cent of the people are asleep in their beds?

Logically you could drive thirty miles in one hour at 30mph or you could do the same journey in one and half hours at 20mph. At least I am honest enough to say I would drive at a speed that takes the shortest time.

Would you let a child go horse riding, when you know it would be safer standing on the ground doing nothing? But the very slight risk, is worth the child's pleasure.

The advantageous mobility a 30mph limit provides are out of all proportion to the relatively smaller risk of an accident or injury that 20mph limits provide.
Terry Hudson, Kent

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+1

I do sometimes wonder about your driving style Duncan! Do you find yourself frantically braking a lot? The aim is never to have to frantically brake, but only having to ease-off and come to a stop without any histrionics. The slower the initial speed relative to the road and traffic conditions, the less likely to need to panic stop.
Hugh Jones, Cheshire

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-3

Surely then Hugh the most appropriate output would already be zero as that is the only output state that would make frantic braking completely unnecessary!
Duncan MacKillop, Stratford on Avon

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+3

Moments before accidents, drivers are usually desperately trying to reduce - preferably to nil - the 'measurable output' of their vehicle to prevent contact. Better therefore, to have induced such drivers to have reduced their 'measurable output' in the first place (the input?), to make frantic braking unnecessary.
Hugh Jones, Cheshire

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-1

Vehicle speed is the measurable output from the system. Choking the output does not effect the input yet it is errors in the input stream that cause accidents in the system.

Therefore a decision has to be made as to which is preferable, a choked output with no change to input or a changed input that has some effect on output. Only the latter can make any difference to the accident rate.

So far on this thread and the many similar threads, all the talk has been on the degree of output management because choking output by changing the number on a pole seems to be a much easier task than fixing the input. It is my contention that fixing the input is nowhere near as difficult as it might appear, but that fix does require a radical change in the way that people think about the problem.
Duncan MacKillop, Stratford on Avon

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+2

Derek

My first comment was correcting my quote in the article and adding some context. I trust that this was useful.

My second comment was a response to Idris Francis claiming that "my signs had been illegally placed".

My third comment was responding to Idris again and explaining that if they were "metal signs" then they had not originated from us.

I believe that such responses were perfectly reasonable and in the spirit of open debate.

I would trust the moderator to moderate as appropriate.
Rod King, 20's Plenty for Us

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-4

Note quoting Nick Rawlings:

" . . we are encouraging contributors to state their views once and then allow others to do the same . ."

I count three from Rod King so far out of nine comments.
Derek Reynolds, Salop.

Agree (12) | Disagree (2)
+10

"20mph can reduce collisions" I'm sure it "can", just as 10 mph might be able to, or 5, or 1, although I'm not sure it actually does. Surely there is something missing in this simplistic equation? What about pushing accidents elsewhere, increasing driver fatigue, and conflict, as many simply cannot be bothered to drive so ridiculously slowly where there is clearly no need? Increased emissions and congestion? False perception of better safety? Many 30 limits are ignored, surely there needs to be some more intelligent and effective work to find out what the real problems and solutions are, rather than putting up a few number 20's and thinking everything is wonderful. Quite apart from the fact that anyone needing the number 20 to drive safety where such a speed is necessary is not fit to be driving anyway.
Dave, Guildford

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+6

Idris
It's interesting that you say the "offending signs" are metal. Then either a batch of our wheelie bin stickers have been miraculously converted from "base vinyl" into metal or they have originated from some other source than ourselves.
Rod King, 20's Plenty for Us

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-2

Here in Somerset, particularly, it's a fair generalisation that if you keep to BUA speed limits you will be the slowest kid on the block and increasingly, not only do drivers follow very closely but, in their frustration, they are more likely to overtake you, quite often in inappropriate conditions. I am not saying that I condone their behavior, merely that there is no effective deterrent to it. Roads policing is more or less non existent except on one or two major roads and occasionally on the motorway.
Nigel Albright

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+10

Rod:
I think I can safely say I have forgotten more about statistics than you have ever known, which is one reason I have long been calling for more data to be made available from existing 20mph areas. That said, my detailed analysis of Portsmouth's "success" shows much worse SI trends.

The two 20's Plently signs near here, that I am in the process of having removed because they are illegal, are in fact metal.
Idris Francis Fight Back With Facts Petersfield

Agree (11) | Disagree (7)
+4

Idris

You know very well that statistics based on the small number of KSI's is statistically unsound. It needs a careful analysis of disaggregated data to separate out anomalies.

What is very comforting to 20mph campaigners is that wherever 20mph has been piloted then such an analysis always supports further roll-out and implementation.

You seem to have a focus on a few plastic stickers that you pass on your travels. Don't worry, I and the millions of people around the country who support lower speeds for residential roads are working hard to get as many of the proper permanent metal ones installed instead.
Rod King, 20's Plenty for Us

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-1

It is not total collisions that matter, but fatal, serious and slight collisions separately. There is some evidence that while overall totals may fall, serious accidents rise. Someone has to balance one against the other but 20mph advocates prefer not to.

Rod - you missed another opportunity to confirm that you will ensure that your signs illegally place on "street furniture" will be removed.
Idris Francis Fight Back With Facts Petersfield

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+6

For the record, my actual response to the report as communicated in our press release was:

"Transport consultants SDG are clearly in favour of adoption of wide area 20mph limits. We know that it’s popular with residents too. Explaining the benefits to drivers is key to lasting cultural change where 20mph makes places better places to be. Local and national politicians can be confident that 20mph is a clear win-win for their residents, communities and the country. It’s time for 20 to be the default limit for not only London but all our urban, village and community streets."

Our full press release, which sees this as a very positive report for 20mph limits, can be seen at:
http://www.20splentyforus.org.uk/PRel/SDG_Advise_20mph.pdf

In addition ETSC (European Transport Safety Council) also called for 30kmh (20mph) as a maximum limit or all residential streets and where there were high levels of pedestrians and cyclists throughout the EU.

Our press release on this may be seen at:
http://www.20splentyforus.org.uk/PRel/ETSC_20mph_call.pdf
Rod King, 20's Plenty for Us

Agree (8) | Disagree (12)
-4

I think that the first statement that "reducing vehicle speeds results in fewer and less severe collisions" is very much a controversial issue. Whilst it can be argued that at a slower speed the amount of impact will not be as great as if the speed were faster. The fact that collisions are reduced has not yet been born out. The jury is till out on that statement. I know that I may appear to be against 20 mph but I am not. Where it has been implemented locally I have adheared to it.
bob craven Lancs .... Space is safe Campaigner

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+7

The headline sums it up really - the principle of 20mph limits in residential roads is a no-brainer, but if actual vehicle speeds do not reduce accordingly there will be no benefit. Securing compliance is the key.
Hugh Jones, Cheshire

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