Do the stats really say that twenty is plenty?

By - Wednesday 27th May, 2015

Robert Ward has got his data hat on again, and this time he’s keeping his eyes on the road

Croydon Council is consulting again. This time it’s a proposal to implement a 20 mph limit on most of Croydon’s roads.

Following my complete failure to affect the outcome of a previous consultation (on landlord licensing), I was inclined to move swiftly on, especially as this is an issue on which I had no opinion. But my eye was caught by the assertion that “research and evidence has demonstrated clear benefits from lowering speed limits in residential areas”.

Similar claims were made for landlord licensing, where I found there was in fact no evidence. Perhaps this time the claim might prove more substantial, and unencumbered by a pre-formed opinion I could be more objective. I decided to have a look.

Which of these statistics is relevant, and do any of them justify the proposal?

The council documents offer little. Other than cost, only benefits are mentioned and of these, an improvement in road safety is the only one that might be measurable. The others – discouraging passing through traffic; encouraging walking and cycling; improving the local environment – are arguable but not easy to measure.

Some unsupported statistics are quoted. Research from the Royal Society for Prevention of Accidents concluded, unsurprisingly, that a pedestrian struck at 20 mph has a better chance of survival than if struck at 30 mph. Department for Transport (DfT) research showed that every 1 mph of average speed reduction achieves a 6% reduction in accidents.

As to financial impact, a DfT estimate that the average cost to society of an accident is £68,320 is multiplied by the 889 accidents in Croydon in 2013 to derive a loss to society of some £60 million. No references are provided for any of these figures.

So let us play devil’s advocate here. Which of these statistics is relevant, and do any of them justify the proposal?

The figure of £60 million is entirely bogus

That getting hit by a car travelling at 20 rather than 30 mph is less likely to be fatal is a statement of the obvious, but not necessarily relevant. I could find only one death in the last five years in the area of North Croydon which is currently out for consultation. This was a sad case where a man accidentally ran over his wife at the end of their driveway while checking the brake light.

The estimate of a 6% reduction in accidents for every mph reduction in average speed is useful, though it warrants investigation as to how it was calculated, as does the estimate of the average cost of an accident.

The figure of £60 million is entirely bogus. Even accepting the base figures as correct, this is the gain if we were able to eliminate all accidents within the Borough. Reducing the limit on some, but not all roads will never achieve that. Main roads, where most accidents occur, will still have a 30 mph limit.

I was unable to find the source of the 1.3 mph figure

Although both are at the high end of what I was able to find in the published literature, the 6% reduction in accidents per 1 mph speed reduction, and the estimated cost per accident, are in line with other research. However, they are only relevant if what is planned actually reduces average speeds and/or collisions.

A similar scheme implemented in Portsmouth in 2008 did indeed show a statistically significant reduction of 21% in casualties. However, over the same period, casualties reduced nationally by more than 12% anyway. Could it be that much of this reduction, if not all of it, would have happened anyway? Indeed, an independent report concluded the difference was not statistically significant.

As to reductions in average speed, I was unable to find the source of the 1.3 mph figure. The same independent report already mentioned found a reduction of 0.9 mph, but concluded that this was not statistically significant.

We should also ask how similar Portsmouth is to Croydon. Portsmouth found different results dependent on the prevailing traffic conditions in the area. A statistically significant reduction in average speeds of 7 mph was only observed where average speeds before the scheme was introduced were greater than 24 mph. Portsmouth was able to identify these areas because they had extensive data on traffic speeds. Croydon has no such data, although mention is made that it is being gathered, but only after the decision has been made.

Public information was limited and exclusively supportive. Analysis was non-existent

Some years on from the Portsmouth implementation, there is anecdotal evidence that the initial positive results from the scheme were not sustained. This is thought to be because the scheme, as with the Croydon scheme, consisted of putting up signs but no additional enforcement.

So can we conclude whether the Croydon scheme is value for money? We have only looked at one possible benefit of the scheme, and from this analysis the answer is that we really don’t know. However, there are other possible benefits which may make the case.

Of more interest to me is what this says about the consultation process. Public information was limited and exclusively supportive. Analysis was non-existent. In the relevant cabinet meeting, assertions were made on the efficacy of 20 mph limits for which I can find no evidence.

All of which leaves me to question the decision-making process. More worryingly, it makes me wonder what a consultation is meant to achieve.

Robert Ward

Robert Ward

Engineer and project manager specialised in helping businesses make better strategic decisions and improve safety, quality and effectiveness. Conservative Party Councillor representing Selsdon and Addington Village on Croydon Council. He tweets as @moguloilman.

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  • David Callam

    A consultation by a public body is a device designed to support the prejudices of those in a position to influence the device. I’m surprised you’re surprised.
    This consultation will be unequivocal in its support for 20mph speed zones in the north of Croydon. No, I’m not clairvoyant, just somewhat cynical

    • Anthony Miller

      “that might upset too many drivers, all of whom are also voters”

      How inconvenient

  • Anne Giles

    It just means that a trip into Croydon will take longer. At the moment I have to calculate 3/4 of an hour to get from here to Croydon University Hospital, as well as trying to find a disabled bay to park. It will take longer, as I do travel along the smaller roads, the main one being full of traffic. Driving into London through 20mph areas (Dulwich, Camberwell, etc.) is a nightmare, as it means crawling through traffic jams and the consequent back pain.

    • ScaredAmoeba

      “It just means that a trip into Croydon will take longer.” – Not significantly.


      • Anne Giles

        I don’t read links anyway. However, I would point out that on the occasions when we have had to drive into London, the routes with 20 mph speed limits have slowed us down tremendously. We now avoid routes going through Dulwich, Camberwell, Elephant & Castle, but go via Tooting and Wandsworth Bridge instead. On longer journeys like this, the journey takes an awful lot longer. A journey to Stoke Newington took us 2.1/2 hours. Journeys into the centre of London at least 2 hours. Sitting in cars for that length of time affects my back and the pain can be unbearable. I am unable to use public transport.

        • moguloilman

          20 mph limits make a difference to accident rates mainly by slowing down traffic. If the lower limit does not slow down traffic then it was a waste of money to put the signs up.

          The limit on more important roads is generally not being altered. Journeys may be slowed somewhat on these roads by cars being displaced from the 20 mph roads onto the unaffected roads. This is part of the price we pay. Proper analysis would understand this and balance the pros and cons.

          You have pointed out a possible downside for you personally. One could argue about how much of a delay might be caused by the 20 mph limits but in the end, sadly, few if any decisions have no downsides.

          • Anne Giles

            How right you are!

          • Anthony Miller

            “The limit on more important roads is generally not being altered”

            Again this is not true. TFL have also introduced 20mph zones on what they regard as dangerous sections of road. Furthermore Rod King is absolutely clear that his end political aim is 20mph on all urban roads instead of 30mph. Cllr Sean Fitzsimons has said the same thing. Anyone who doesn’t take this at face value is a fool. They are totally open about their long term political aim. Until, of course, they are forced by law to go through the tedium of a consultation. I don’t know why anyone bothers to discuss it. The political class have decided we will all now be driving at 20 …what anyone else thinks about doesn’t really matter.

        • angus_fx

          Everything between Camberwell and Haggerston has been miserable to drive during the day for quite some time – long before 20mph limits were introduced. Walworth Road has been one big traffic jam since the 90s.

          At 1am when the roads are empty(ish)? Croydon to Stoke Newington in under an hour, even at 20. It’s not the speed limit, it’s the traffic.

          Is public transport really not an option even with taxis at either end? The Overground from W Croydon, Norwood Junction or New Cross (change from an East Croydon semi-fast) will get you within a £10 cab fare (or a 15-20 minute walk, if that’s an option) of Stoke Newington. (Norwood Junction isn’t step-free, the others are). Or take a fast to London Bridge, there are lifts to the Jubilee line there, change at Canada Water (step free again) and Overground to Dalston Junction.

          TfL Journey Planner says ~45 minutes East Croydon to Dalston Junction via New Cross (which they’ve just rebuilt with lifts), the cab ride from there is another 10-15.

          • Anne Giles

            Thank you for trying to help. I used to take the train to London Bridge and the Jubilee line to some parts of London, as it is step free. Unfortunately, I can no longer walk from the Fairfield car park to the train at East Croydon. I can’t stand at bus or tram stops because of the pain in my spine. Taxis are fairly unaffordable, now that I am retired. I can’t do a 15-20 minute walk now either. Just manage 20 metres! Thanks anyway!

      • Anthony Miller

        “Not significantly” who are you to decide what is signficiant in my life? If you reduce death by forcing everyone who drives into a form of living death because they have to spend more time on the road than they need to then that is a form of death too – it is death by boredom.

  • lizsheppardjourno

    An interesting and difficult read for me, because as a parent I’m desperate to slow traffic and create safer streets. Traffic is my biggest fear for my children who now go about unaccompanied on a daily basis. I’ve always tried to be un-hysterical about the risks they face – they are extremely unlikely, for example, to be abducted – but hit by a car? Oh yes. One moment’s inattention by the dreamy, unfocussed teens and they certainly could be, and the speed at which it is moving could be the difference between life and death.

    It’s important that we make evidence-based, rational decisions and use scarce public funds wisely. But I still instinctively want all traffic, other than on motorways and dual carriageways, to move much more slowly – and this proposal goes some way to meeting that wish, making it hard to oppose. I’m sure I’m not alone in that.

  • Austen

    It’s a pity that the author and negative commentators hadn’t delved a little deeper before putting, metaphorically speaking, pen to paper.

    The subject of 20mph limits was discussed in depth at Croydon’s Streets & Environment Scrutiny Sub-Committee meeting on 16 September 2014. Labour and Conservative councillors were present, and contributions to the debate were made by the 20′s Plenty for Us charity, Croydon Cycling Campaign, Living Streets (formerly the Pedestrians Association), the Metropolitan Police, the Institute of Advanced Motorists, the Alliance of British Drivers and members of the public.

    The figure of £60 million is not “entirely bogus”. It reflects the government’s Department of Transport’s “Average value of prevention per reported casualty and per reported road accident” cost figures applied to Croydon’s road casualties in 2013.

    A long-term study demonstrating the benefits of 20mph zones was published by the British Medical Journal using data on London roads between 1986 and 2006. This found that the introduction of the 20 mph zones was associated with a reduction in casualties and collisions of around 40 per cent.

    Whether it be put in financial terms, or the hidden but real cost of human misery, the bill for doing nothing to make Croydon’s roads safer is too high; in 2013, more people died on Croydon’s roads than were murdered.
    20mph, properly introduced and enforced, will make Croydon’s roads safer for everyone.

    • Stephen Giles

      I think that if a £1,000 fine for motorists – including cyclists, who frequently overtake me towards Addington on Gravel Hill when travelling at 40mph, for exceeding 30mph where enforced, would achieve farm more than introducing a 20mph speed limit. A road awareness test should also be compulsory for cyclists.

    • Stephen Giles

      And the money is available “to properly enforce” a 20 mph speed limit is it?? I don’t think so, I must say.

    • Anthony Miller

      “Whether it be put in financial terms, or the hidden but real cost of
      human misery, the bill for doing nothing to make Croydon’s roads safer
      is too high; in 2013, more people died on Croydon’s roads than were

      This has always been the case. It is an irrelevant statistic. Neither are Doctors experts in road traffic safety. Actually the number of all time accidents is at an all time low. To quote Professor ofGeography Danny Dorling of the 20′s Plenty campaign “the number of people dying from road deaths is not on the increase but due to a decrease in other forms of death then the fear of road death has increased accordingly as road death is now a greater percentage of total deaths”.

      The 20′s plenty campaign is an expert lesson in the manipulation of the psychology of fear. There will always be road deaths because there have always been traffic deaths no matter what form of transport is used. People used to drown in the age of water transport and be thrown from horses in the days of equine transport. Even if you could reduce the risk of injury and death to zero would it actually be a sensible thing to do? Is not increasing everyone’s journey times just replacing literal death with a form of living death where everyone’s bored to death?

      • Austen

        “Even if you could reduce the risk of injury and death to zero would it actually be a sensible thing to do? Is not increasing everyone’s journey times just replacing literal death with a form of living death where everyone’s bored to death?”

        Great timing. Written 24 hours after 5 people – including 4 children – were hit by what eyewitnesses say was a speeding car. 2 of the kids have since die. Written just 4 hours after a woman was killed for the crime of riding a bicycle to work in central London. Written by someone who appears to be out-of-touch, insensitive and selfish.

        Funny, ha ha? No. Funny, peculiar.

        • Anthony Miller

          People will never stop dying on the road so if you wait for it to stop before having an opinion you will wait forever.

          • George

            That’s impressively unimaginative.Why will people ‘never stop dying’ exactly?

          • Anthony Miller

            According to British Road engineer J J Leeming’s famous 1960s analysis of historical data for British transport fatality rates there were 470 deaths on the road per million population per year in 1863-1870. This breaks down as 76 rail, 143 road and 251 water deaths per million population. The first proper motor cars came in in 1886. So even before the car was invented roads were dangerous compared to today. It doesn’t follow that even if you could completely abolish cars you could prevent road accident deaths. Therefore unless you actually stop people moving there will never be a stop to road deaths. Road deaths were much higher in the 1930s than they are today despite there being less cars. There was a massive peak of road deaths during the war due to the blackout and there was a massive peek in the 60s-70s due to the explosion in mass car ownership… since then road deaths have been in continual decline from a peek of about 8000 to less than 2000 today …so that’s about 29 road deaths per million population today. You will ‘never stop dying on the road’ because history shows that road accidents/deaths are part of life. They can be minimised but they can never be completely eliminated because it is not possible to forsee every possible situation. Theoretically there should be no rail accidents because it is possible to know exactly where all trains are all the time but of course there still are rail accidents because of human and computer error. Therefore you can never completely stop people dying on the road and if you were to wait for this to happen before having an opinion you would of course in practical terms be waiting forever.

    • ilPugliese

      Will it though? In our area, soon to be twentied, there have been zero serious or fatal accidents in the 18 years for which data is available. I don’t think that can be improved on. Nearly all such accidents are on main roads. Perhaps the BMJ study you refer to could be made available, so that we can check through the data on specific accidents.

      • Austen
        • ilPugliese

          Thanks for your prompt response. I have not had time to go through it yet because of Christmas, but I will shortly because we have a public meeting next week on the proposed blanket 20mph zone in South Croydon. Looking at for the area, the comparison between main roads (As and Bs) and side roads is quite dramatic. Almost all the serious and fatal accidents have been on the main roads. Yet the target of the 20mph zone is the side roads.

          • Robert Ward

            The BMJ report is indeed an excellent report and an interesting example of how geographical data can be combined with other data.

            Your remark on where the crashes are gets to the heart of my main point – if the speed is already below 20 and there are no accidents then a 20 mph zone costs money for no benefit. Indeed you put more unsightly obstacles and distractions on the street. The money is better spent elsewhere. The council is less worried about that because it appears the money comes from tfl so as far as Croydon Council is concerned it’s free money.

            I live in South Croydon but had not heard of this public meeting. The lumping of a bunch of areas together and lack of publicity makes it sound like they just want to rush it through.

          • ilPugliese

            The meeting has NOT been organised by the Council! The date and location are 7.30pm – FRIDAY JAN 6, 2017 – Coulsdon Community Centre. Details are near the bottom of this link – you may have to click to include more comments.

  • moguloilman

    I would ask zealots, both for and against, to read my words carefully. I do not make a judgement on whether 20 mph limits are a good or bad thing. My conclusion based on looking at one aspect is that on the evidence presented for the particular case in North Croydon under consultation we don’t know. However, the three other positive aspects may make this a good decision.

    On specific points:-

    There may be many other studies, but my experience, which I try to illustrate in my articles, is that the evidence is selectively quoted, poorly analysed and difficult to find. It should also not be up to me to find it. Any proper justification should show references to data sources.

    A concern for ourselves and our children is that a 20 mph limit must be a good thing so how could you possibly oppose it? Opposition is too strong a word, but if it makes no difference, for example if the traffic in these streets is already going less than 20 mph, then it is money spent to no benefit. It may make you feel better (which is not nothing), but it may not make any difference.

    The figure of £60 million is bogus. It is the result of multiplying two numbers together to show a big number. The vast majority of Croydon’s accidents occur on roads that will have an unchanged speed limit. A number that might have some justification as an upper bound for benefits of the scheme would be to take only those accidents that occurred on the roads that will have a reduced speed limit and multiply that by the average cost of accidents on that type of road. This would give a number an order of magnitude lower, perhaps even less than that.

    • Austen

      “The vast majority of Croydon’s accidents occur on roads that will have an unchanged speed limit.”

      I’d be interested in seeing your evidence to back that claim.

  • ScaredAmoeba

    The source of the “6% reduction in accidents per 1 mph speed reduction” I suspect was this: “1 km/h increase in speed → 3% increase in accidents.
    In practice the relationship is more complex. The exact relationship depends among many other things on speed level and road type. The higher the speed, the steeper the increase in accident risk”


    And follow the references.

  • ScaredAmoeba

    20 mph limits are supported by lots of literature. Aside from the aspects of impact survival, collisions with children are more likely.

    Reduced Sensitivity to Visual Looming Inflates the Risk Posed by Speeding Vehicles
    When Children Try to Cross the Road John P. Wann, Damian R. Poulter, and Catherine Purcell

    Almost all locomotor animals respond to visual looming or to discrete changes in optical size. The need to detect and process looming remains critically important for humans in everyday life. Road traffic statistics confirm that children up to 15 years
    old are overrepresented in pedestrian casualties. We demonstrate that, for a given pedestrian crossing time, vehicles traveling faster loom less than slower vehicles, which creates a dangerous illusion in which faster vehicles may be perceived as not
    approaching. Our results from perceptual tests of looming thresholds show strong developmental trends in sensitivity, such that children may not be able to detect vehicles approaching at speeds in excess of 20 mph. This creates a risk of injudicious
    road crossing in urban settings when traffic speeds are higher than 20 mph. The risk is exacerbated because vehicles moving faster than this speed are more likely to result in pedestrian fatalities.

    • Anthony Miller

      “20 mph limits are supported by lots of literature” That’s because Rod King produces industrial quantities of it. Unfortunately the statistical data is poor to sketchy. What about in Portsmouth where after the introduction of a blanket 20 zone the number of deaths seemed to increase, the number of accidents decrease and the speed of traffic hardly change at all…

      • ScaredAmoeba

        “20 mph limits are supported by lots of literature” That’s because Rod King produces industrial quantities of it. – Sheer, disingenuous, mendacious nonsense, spread by those with an axe to grind. Just because Rod King reports facts you don’t like, doesn’t make his claims untrue.
        The relationship between speed and survivability is well known. The BBC’sMoreOrLess revealed the story was full of holes.

        • Anthony Miller

          An interesting graph but Ashton and MacKay are not the only source of data. As you can see from this page

          if you overly all the different graphs you get very different rates of increase. There is more than one function you can fit. That one I believe is Pasanen’s

          1991 paper. Without any error measurements the graph is meaningless….

          There probably isn’t a “right” answer to this as it depends on what data you include/exclude ..what functions you fit and whether or not you bin your data. What Ashton and Mackay created is a statistical model based on empirical data … but that kind of isnt the point, is it? I honestly don’t think there’s a right or wrong answer to this because it depends how you weight up freedom of movement vs freedom from the statistical probability of death or injury. People like Wolmar actually believe that there’s no situation where any even accidental death is acceptable. They genuinely pursue a ZERO Deaths policy. Fine …if society’s happy to pay for that but …practically realistic?

  • moguloilman

    Some more responses to points raised.

    I most definitely do not say that 20 mph limits are a bad thing or that there are not many circumstances in which the reduction in accidents has been shown to be statistically significant and the reduced limit cost effective.

    What I do say is that there are circumstances where there is insufficient evidence to show that there is a statistically significant reduction in accidents. There may still be other reasons that would justify imposing the 20 mph speed limit, some are listed in the article.

    Reducing speed reduces accidents but if the imposition of the 20 mph speed limit does not reduce speeds then it will not reduce accidents. If speeds are already less than 20 or so mph then you might still want to impose the lower limit for the other reasons listed in the article but this imposition is not justified on the basis of reducing accidents alone.

    The evidence is that if average speeds are already low, or if the accident frequency is low then the 20 mph limit is either not justified (at least not on the basis that it reduces accidents) or is not the most cost efffective means of doing so. A weakness of the Croydon justification that is out to consultation is that there is no information on what the current average speeds are, and as far as I can find no-one has looked at the accident frequency on these roads.

    On my failure to find every last article and number. It took me some considerable time to find what I did find, but in my view that should not be up to me. The consultation information, as I point out, consists of a couple of pages that are wholly positive and contain no references. It should be a lot easier than that.

    Lastly, I have read several new articles pointed out by those who have commented. I was unable to access the BMJ article quoted (it costs money) but I believe I was able to access information from the same authors which shows the same analysis. None of the new information I have read refutes the arguments I have made.

    • Austen
      • moguloilman

        I think I have read enough evidence for the moment. Besides, I find that your paper is largely made up of assertions (“it is generally accepted etc….”) and links to other documents that make similar assertions.

        I think it is time that you addressed some points, for example:-

        There are circumstances where a 20 mph limit is not effective in reducing accidents and others where it is not cost effective.

        There is no analysis that shows whether the area of Croydon North where this is planned to be implemented soon fits these criteria or not.

        Most accidents in the above mentoned area occur on roads which will remain 30 mph roads. Therefore the £60 million figure for Croydon is a wild exaggeration of any benefit that might accrue.

        • Austen

          Looks like you’ve chosen to ignore the references to various articles I quoted, including detailed studies. I can’t help that, but to then suggest that my paper is “largely made up of assertions” is both wrong and hypocritical; what’s the basis of your counter arguments, other than your opinions?

          • moguloilman

            I did look at the various articles and I repeat that I found nothing which refuted any of the following:-

            If traffic goes slower on urban roads, then, other things being equal there are likely to be less accidents. YES.

            Can a 20 mph limit as planned for Croydon be effective under some circumstances in reducing accidents. YES.

            Are there circumstances in which a 20 mph limit like this will make no measurable difference. YES.

            Are there circumstances in which a 20 mph limit like this is likely to reduce accidents but is not the most cost effective way of achieving this reduction. YES.

            Do we know which parts of Croydon are those where this limit will be effective, which parts it will not be effective and which parts it will have some effect but there are better alternatives. NO.

            Please advise which of these you believe is wrong and the specific evidence supporting that view and I will do my best to respond.

          • angus_fx

            Perhaps one other salient question:

            Is there a survey, knowledge resource or statistical method which will find out the answers to those tricky questions, definitively and reliably, for significantly less cost than actually just implementing it and measuring outcomes?

            However, if that is to be the approach – and I suspect it’s not a bad one overall – it is at least worth making sure there is a solid programme of measurements in place which correspond to clearly stated goals.

            Other boroughs have rolled out their entire 20mph programme for as little as £300k. So perhaps not a very expensive experiment, in the grand scheme of local authority budgets.

          • moguloilman

            The data sets that are available are not many but much of it is around correlations between speed and number of accidents and their seriousness. The data suffers from not having any before and after speed measurements. The missing piece is what impact imposing a 20 mph limit might have in reducing speeds.

            The Portsmouth data is the one I looked at in detail and it showed the reductions in speed on various types of roads and conditions. If it were me I would measure speeds in a zone that is a candidate for a 20 mph limit and see if it fits into the speed and traffic pattern where such a limit might be successful.

            I think I read that Croydon plan to do some measurements. Whether it is before AND after I don’t know. I don’t think there is any intention to stop the implementation so even if retrospectively you found that the area was unsuitable there would be no point in spedning the money to revert to the original limit.

          • angus_fx

            It gets more complex still.. if the council ultimately wants to reengineer certain roads to make them 20-friendly, the process is something like.. 1) establish a democratic mandate that the road ought to be 20, 2) implement the limit, 3) measure the outcome, 4) if further engineering measures are needed, adopt them.

            It’s reasonable to argue that if the outcome they want is for traffic on those roads to move at 20mph or less, they might skip straight to 4), but it’s hard to know for sure what compliance will be like.

            The ultimate objective is a self-enforcing social norm, for that to work the scheme has to be easy to understand (either blanket 20, like Southwark, or “A”-roads excluded, like Croydon), which in turn implies it will encompass some roads that are going to need additional engineering (hopefully not in the form of speed humps) to become self-enforcing.

            Which in turn means it’s not /necessarily/ a bad idea to support the introduction of 20mph limits on roads which don’t seem immediately suitable. Step one on a longer process.

    • ScaredAmoeba

      “It took me some considerable time to find what I did find, but in my view that should not be up to me.”
      It took me very little time.

      • moguloilman

        You may be more familiar with the subject or just faster, luckier or smarter than me.

        I would point out that although I have been pointed at lots of new information, none of it has altered the substance of the article.

        • ScaredAmoeba

          “none of it has altered the substance of the article.” On the contrary, it has torpedoed your questionable rhetoric, by revealing it as unjustified.

          “Of more interest to me is what this says about the consultation process. Public information was limited and exclusively supportive. Analysis was non-existent.” – This is untrue. There is an unjust and unwarranted implication here that there’s some hidden agenda. Digging deeper, reveals this research and analysis has already been done by relevant experts.

          To suggest or imply that one Council should repeat this research and analysis is in-effect a suggestion that all Councils similarly engaged in improving road-safety should do likewise. That must be seen as a strong warning sign that your argument should be seen for what it is – an argument intended to delay, postpone and obstruct – it is a covert NIMBY argument, but what a ridiculous waste of money that would be. Doubtless you also complain ceaselessly about wasting taxpayers’ money. Many might view this as arrant hypocrisy.

          Far better that the analysis is done once (it has been replicated by other study groups in other countries with similar results)

          • moguloilman

            I have yet to see any of my arguments torpedoed. Please see my list of questions and my answers shown above.

            Regarding the process of approval by the Council, I was only able to view the recording of the Cabinet meeting, which consisted of one or two reasonable questions on implementation which were responded to but not answered by political point scoring. On the Scrutiny Committee I was able to find documents but did not find evidence of adequate challenge.

            Regarding the consultation, the consultation document is two pages, all of which is supportive. I am unsure what I am being asked. It seems to me that it says – we have made this decision and it’s all great, scream if it causes you pain, find the evidence yourself, if you can.

            I would like reassurance that it is the right decision for Croydon and I can find nowhere anything that tells me that (see my list of questions again). I am not suggesting that research needs to be repeated. I do think it needs to be challenged and its relevance to the Croydon situation assessed.

            It is most certainly not a NIMBY argument or that I think that Councils routinely waste money. It may be the case in my area that 20 mph limit is justified, but at the moment I just don’t know.

            On the question of the money, the Council is elected to govern. Spending money wisely is what they are elected and paid to do. To do that job they need to understand the evidence, challenge it appropriately, decide what is in the best interests of the people of Croydon and then implement it effectively. I would like to see that this is happening.

            I am agnostic on whether 20 mph goes though in my area. We have speed bumps that make me think it won’t make much difference but I would need to look. If I had to choose a change in traffic patterns, for me it would be to prevent the occasional large articulated vehicle going through. My posbox at the end of the street was only repaired yesterday after being knocked sideways by one such. The driver just drove on.

            You might also like to think about possible decisions with which you would disagree. How would you like it if a decision you did not like went through without proper process?

          • ScaredAmoeba

            ” have yet to see any of my arguments torpedoed.” – Nice bait and switch. I quoted you “none of it has altered the substance of the article.” I responded: “On the contrary, it has torpedoed your questionable rhetoric, by revealing it as unjustified.”

            “Of more interest to me is what this says about the consultation process. Public information was limited and exclusively supportive. Analysis was non-existent.” As revealed this is also untrue.

          • moguloilman

            I was somewhat baffled as to what you are talking about it, but I think I may have figured it out. Your point seems to be that not all information in the public domain is totally positive and that some analysis is available in the public domain. By public domain I mean it can be found somewhere on the internet or in a library. If so, I agree.

            Myconcern is that it is not enough that there is a range of knowledge and analysis somewhere in the public domain. If I am presented with a decision (as the Council are) then that information needs to be balanced, it needs to be challenged, it needs to be analysed, and a decision made in which the pros and cons are weighed in the context of Croydon. That is what the Council and the Council employees are paid to do. As a voter I expect to be able to see this is happening, both when the decisions are being weighed and retrospectively.

            As a resident, I am now being consulted. My problem is I am not sure what I am being consulted about. The decision has been made. I am not being consulted about that. Or am
            I? Am I being consulted about whether the policy will be applied in my neighbourhood? Possibly. Am I being consulted about how it is applied in my neighbourhood? Possibly. If not any of these, then what?

            If it is about whether or how it is applied in my neighbourhood then I expect the information and analysis to be presented to me in a balanced way so that I can make my judgement and give a reasoned response. I also want to see the Council’s
            thinking on why they back the decision. A two page document that is entirely positive does not do that.

            I am even less convinced if I see that the Council meeting that approved the plans had a completely sterile debate. The leader of the Council said that what convinced him was the fact that a person hit at 30 mph is much more likely to die than someone hit at 20 mph. Not only is this a statement of the blindingly obvious, it misses the point. The point is will putting up 20 mph signs in parts of my neighbourhood make any difference. I still don’t know, and what is more, I am not convinced anyone else does either.

          • Austen

            Robert, that you “did not find evidence of adequate challenge” at the Scrutiny Committee, despite the presence of opposition councillors and speakers from groups hostile to 20mph might suggest that there was nothing of worth they could find to oppose the proposal.

  • Dave

    Travelling at 20mph is an unbearably slow and frustrating experience which contrary to the councils belief will increase pollution and be of negligible benefit to decreased car use. The council has provided accident statistics for 2013, highlighting 284 involving pedestrians and cyclists (combined) and 562 involving cars. Will 20mph reduce these statistics? I think it depends on the actual causes of theses accidents. What would be more beneficial is an in-depth analysis of the causes of these accidents themselves instead of just telling us the numbers. For example, where they caused by a lapse in concentration by a pedestrian/cyclist/driver? Was it down to misunderstanding of signage? Did someone do what they were not supposed to do – ie cross where they shouldnt, break a stop sign/light etc. Or as Robert mentioned, was it a case of misadventure being ‘recorded’ as an accident. In other words, how many of these accidents were actually found to be caused by a vehicle travelling at 30mph? That would be of more relevance than just giving us blanket statistics.
    In my experience, (I have been a pedestrian, cyclist,bus user, moped rider and driver for extended periods of my life so far), travelling more slowly could in fact be less safe. There have been hundreds of times where I have seen pedestrians cross roads like they are walking in the park because they think the car approaching will not reach them in time, or crossing roads (intersections) without even looking behind them to see if any cars are are about to turn – Not to mention the ones ‘zombie walking’ on their mobiles! (Yes, pedestrians have a responsibility to travel safely too). Similarly, with cars too, many drivers will pull out at junctions if you are approaching at a speed they deem ‘slow’, which can increase the risk of an accident.
    I am by no means pro car, I just think that the 20mph limit should be imposed in roads that really do need them, for example, narrow residential roads, or accident blackspots etc. and only after a micro analysis of the road conditions, traffic levels and other relevant factors.
    Case in point – Some may be familiar with the stretch of road Herne Hill/Denmark Hill between Brockwell park and Kings College Hospital. This road is a very wide road with the additional safety of bus lanes along much of its length. Pedestrian traffic is very minimal, but yet there is an entirely unnecessary 20mph limit along this entire length!

    • angus_fx

      Croydon’s scheme is minor roads only – if it’s slow and frustrating, use the main roads. Although there’s plenty of unbearably-slow-and-frustrating on those, regardless of the limit.

      Southwark (who control the road in Herne Hill) have taken a different approach – they believe that blanket 20mph is easier to understand & better from a compliance point of view; a lot of their high streets are also major A-roads with very high pedestrian and cycle casualties. They and others want to change the norms around acceptable speed in built-up areas (in the same way as the norms around seatbelts, alcohol etc. have changed over the years) – in part, 20 just feels slow if you’re used to 30 (same as 40 feels slow right after you pull off the motorway). In terms of getting from A to B in a reasonable time over urban distances, it’s probably fast enough (10 miles in half an hour?), but it does _feel_ slow, sure.

      • moguloilman

        An advantage of different Council’s taking different approaches is that it gives us the chance to see what works. Gathering data to enable us to talk about facts rather than opinions really helps although from what I can see that doesn’t often happen.

        Context is important so Soutwark may have very different traffic conditions.

        You also have to define what ‘works’ means.

        • angus_fx

          Some data is pretty well gathered – injury collisions, for example.

          Other aspects, moderately well – traffic speeds and volumes.

          The aspects which Croydon’s scheme seems intended to address – public perception of street environment, active travel mode share, subjective safety, children able to travel to school independently etc. – hardly measured at all, and 20mph is just one of a whole raft of measures affecting them.

          From personal experience, South Southwark & North Croydon are pretty similar traffic-wise. North of Elephant & Castle (excellent public transport & C-charge => few private cars, mostly commercial traffic) and south of Croydon town centre (higher speed, lower density, far fewer pedestrians & cyclists), very different story. Cycling mode share is much, much higher in Southwark for a variety of reasons, but otherwise the roads aren’t much different.

          I don’t think Croydon’s scheme is really about the injury collision rate though. While 20 does seem to be fairly effective medicine for that, you don’t cure an illness by applying medicine to every part of the body except that worst affected. There is IMO a strong case for extending the 20 zones to include main roads near schools, designated cycle routes where bikes are sharing the road with everything else, town centres with high pedestrian flows, and known accident blackspots, but they seem reluctant to do so. And of course there’s the need to keep Westfield shoppers happy as they drive in from further afield…

          Partly this is a balancing act: they know rat-running is unpopular & are hoping 20 will reduce it – imposing it on main roads does the opposite. It may also be a test of public opinion – a positive response to 20mph consultations may be seen as an indicator of popular support for reducing car-dominance overall. Additional measures can then be considered for areas with the strongest support, with the council knowing that they’re likely to be popular.

          • Dave

            I agree that 20mph limits would be best implemented where they really do need them: Schools, high pedestrian areas, blackspots etc, A blanket approach like Southwark would be unnecessary overkill.
            Regarding Rat Running, I doubt that would even be discouraged at all or be of negligible effect. People rat run when the the main roads become backed up and travelling through side streets will take less time for them to get to their destination. I assume keeping the mains at 30 will have no effect on present conditions – there will still be queuing traffic in all the same places and at the same times. However, travelling at 20 on the side streets could still be quicker than being stuck in the main road queue. Of course this would be dependent on the actual rat run length and other factors, including driver perception and experiences before and after the scheme. (humps and the like would be more effective at reducing rat running, but of course the cost is prohibitive)

            In this regard, it would be best to analyse current traffic patterns on a road by road basis and implement 20 only where necessary. As you said, apply medicine to where it is needed. Applying measures to areas that dont need it coube be counterproductive and have detrimental knock on effects

    • Anne Giles

      I agree. I am now avoiding the area around Kings College Hospital.

      • Anthony Miller

        Well then the puritans have won haven’t they? Personally every time I see a 20 Zone it just inspires me to drive about town more… the harder they make it the more I see it as a personal challenge. After all if someone doesn’t want me to use a resource it must probably be worth having.

  • ScaredAmoeba

    “Real-world driving tests of the latest Euro 6 compliant diesel cars show they are still more than three times above the EU legal limit for air pollution emissions, according to data compiled by UK company Emissions Analytics.”

    We have to discourage driving in towns and cities, especially residential areas, particularly areas around schools and shops. There needs to be an end to motorised through-traffic. Most people do not need to drive for many journeys.

    Motorists need to pay the full cost of driving. Currently motorists do not. The average registered car in the UK is subsidised by just over 2,000 Euros per year. Motoring taxes fall far short of the costs imposed upon society. The costs of motoring are influenced by the power to weight ratio, mass, propulsion technology, where driven, driving-style and mileage.

    “(2) The findings of this study clearly show that the frequent claim “that cars cover all their internal and external costs” 2 cannot be sustained. Although no detailed estimation of charges and earmarked taxes of cars attributable to external costs has been made in this study, it is obvious that a sum in the range of 300 to 400 billion z of earmarked funds against these costs cannot be reached. On the contrary; it must be stated that car traffic in the EU is highly subsidized by other people and other regions and will be by future generations: residents along an arterial road; taxpayers; elderly people who do not own cars; neighbouring countries; and children, grandchildren and all future generations subsidize today ́s traffic. They have to pay, or will have to pay, part of the bill.

    (3) These findings suggest that political action is urgently needed. The sooner this happens, the more the transition process can be designed in a smooth, efficient, socially acceptable and environmentally friendly manner. The longer that action is delayed, the stricter, more severe and more expensive this process will be.”
    Source: The True Costs of Automobility: External Costs of Cars Overview on existing estimates in EU-27 – Final Report

    TU Dresden
    Chair of Transport Ecology
    Becker et al.
    Dresden, October 12th, 2012

    Most journeys are very short and are easily walked or cycled.

    Average trip length 1995/97-2013
    Up to one mile 21.1%
    One to two miles 18.6%
    Two to five miles 27.7%
    Between 1995/97-2013 of all trips made 39.7% were two miles or shorter and 67.4% were five miles or shorter.
    Note: ’1995/97-2013′ is not a typo.
    Source: NTS0307

    Car journeys, trips per person per year
    Under one mile: 21, 12 passenger
    1-2 miles: 63 driver, 38 passenger
    2-5 miles: 132 driver, 75 passenger
    5-10 miles: 80 driver, 40 passenger
    10 to under 25: 60 driver, 30 passenger

    Vehicle occupancy (commuting, 2013) 1.2ppmv. Single occupancy rate 85%. NTS0906

    • moguloilman

      Sorry, but I don’t have time to look into every claim around transport. I am concentrating on whether 20 mph speed limts are justified for areas of Croydon.

      • ScaredAmoeba

        ” I am concentrating on whether 20 mph speed limts are justified for areas of Croydon.” – Do human beings around Croydon have the same or different vulnerability to impact and air-pollution as anywhere else?
        Are cars in Croydon somehow special, or much the same as anywhere-else?
        Anyone reading your response might conclude that you were attempting to evade answering difficult questions.

        • moguloilman

          The answer to your rhetorical questions is of course yes.

          However I am most definitely not trying to avoid answering difficult questions, I am doing my best to define what the right questions are, and then answer them. Here are what I think are the questions and my view on the answers. I would appreciate your telling me which you agree with and which not.

          If traffic goes slower on urban roads, then, other things being equal there are likely to be less accidents. YES.

          Can a 20 mph limit as planned for Croydon be effective under some circumstances in reducing accidents. YES.

          Are there circumstances in which a 20 mph limit like this will make no measurable difference. YES.

          Are there circumstances in which a 20 mph limit like this is likely to reduce accidents but is not the most cost effective way of achieving this reduction. YES.

          Do we know which parts of Croydon are those where this limit will be effective, which parts it will not be effective and which parts it will have some effect but there are better alternatives. NO.

          I await your views on each of these.

    • Anne Giles

      But why object to subsidising car drivers? Those of us who have no children have to subsidise other people’s children going to school!

      • ScaredAmoeba

        Were you a child once?
        Today’s and tomorrow’s children will be subsidising your driving.

        • Anne Giles

          No they won’t. I pay for my petrol, car tax and insurance out of my own money.

          • George

            I know cars are expensive, but unfortunately they cost society a lot and all the traffic lights and infrastructure aren’t cheap. So much so, each driver is subsidised by £600 a year by the general public.

            “The idea that drivers are “the cash cows of our society” is wrong, the authors write: “On the contrary, it must be stated that car traffic in the EU is highly subsidised by other people and other regions and will be by future generations: residents along an arterial road, taxpayers, elderly people who do not own cars, neighbouring countries, and children, grandchildren and all future generations subsidise today’s traffic.”


          • Anne Giles

            Excellent. Long may this continue.

  • PolarDog

    I did the maths with this regarding journey times for a 5 mile journey. The maximum delay possible as a result of doing 20 instead of 30 is only five minutes.

    This would, however, assume the ability to travel 5 miles without slowing or stopping. Obviously this is impossible in an urban environment.

    Factor in junctions, traffic lights, pedestrian crossings etc. and it’s apparent that the amount of time actually spent travelling at 30 mph is pretty minimal and most of the journey is under 20 mph anyway. 30 mph is only achievable for brief periods.

    Keeping to 20 would barely affect journey time – perhaps 1 minute in five miles – but might save a child or somebody’s pet. Are we all in that much of a rush?

    • Anthony Miller

      I don’t just do 5 mile journeys. I do 100-200 mile journeys. London is 1,572 km² so covering the whole place with 20 zones is bound to significantly increase journey times of anyone who regularly travels long distances. It also works by shoving more traffic onto the few roads which are more or less randomly selected to be 30. A case of the majority subjugating a minority in the deluded belief that this will reduce traffic. It wont. It is a plan for people who never go anywhere to try to stop other people going anywhere designed by fools who think you can socially engineer people out of cars when almost every historical attempt to do this has failed.

      • Austen

        I could point out the many flaws in your “argument” but I doubt you’d pay them any attention.

      • George

        Good thing there’s a great big motorway built for high speed travel then! If fewer people think taking their car through central London is the better option, then brilliant – less pollution (causing tens of thousands of deaths), less congestion (costing the economy billions) and safer streets for all!

        • Anthony Miller

          I need to move equipment into and out of central london and I resent the wasted man hours of driving at 20mph. I also need to drive people who are ill about who can’t travel easily by public transport… I mean it’s okay till you need to carry anything.

          • George

            The average speed of traffic in London is less than 20mph so you lose nothing by there being a 20mph speed limit. All you’d do is rush to get to the next set of traffic lights or traffic jam.


          • Anthony Miller

            Sorry but that’s a huge black lie. If you remove the top speed and lower everyone to the average speed you will of course lower the average speed then you can go through the cycle again remove the top speed and lower everyone to the average speed …right down to zero. Besides which when I drive late at night often from 11pm to 3am because that’s when I finish work you definitely can drive at the 30 speed limit. Isn’t it bad enough that you want to steal months out of my life without treating drivers as too thick to understand the policy which is one of pure bigotted hate of drivers dresses up as safety concerns.

          • George

            That’s the TfL figures, no need to call people liars. That’s the average speed in 2013, before any 20mph speed limits. Months of your life aren’t being stolen away, I promise you.

            Really fella, roads are for getting places, if you really feel you’re suffering from ‘bigotted hate’ [sic] because people want slower speeds so streets are safer, you need to reassess your place in the world.

            Have a nice day, but I suspect that you don’t want to.

          • Anthony Miller

            It’s an obvious lie. Because I know that I don’t drive everywhere at 20mph. Calculating the average for all situations and then telling me then insinuating it must apply to me in every situation and the only reason I think I can drive at 30mph is a delusion is a lie. I know it is because I know I don’t drive everywhere at 20mph. It depends on where you drive and when you drive. So calculating the mean for the whole of London and then saying that nothing will change elsewhere when you lower the speed on all roads to the mean is obviously a lie. It’s a black lie and it’s insulting my intelligence…. which is fairly low to begin with… so it must be pretty obviously untrue.

            I don’t believe the objective is safety. I’ve listened to Rod King, I’ve read the ETA website, I’ve listened to the Councillors and it’s fairly obvious that they are in a state of near paranoia about the motor car and that their read objective is to cut car usage its self for ideological reasons. Yes, I think it is about hate. Roads are a limited resource and therefore between cyclists motorists and pedestrians there is always intense anger about how to best use a limited resource – everyone having violently conflicting and self serving opinions. It is a classic resource war. This is transparent in the ability of for example the cycle lobby to recycle the same flawed arguments such as the one above in the belief that if they repeat them often enough and strongly enough people will swallow them even though they are at variance with their actual experience.

            “if you really feel you’re suffering from ‘bigotted hate’ [sic] because people want slower speeds so streets are safer”

            The cycling lobby endless bangs on about safety and death statistics as if no one’s going round cynically calculating the cost in injury and death vs the cost to the economy of every transport policy and hasn’t been doing this since the begining of time. Of course they have. So it’s not actually rational argument. It’s an appeal to emotion which is a logical fallacy. The aim is manipulate the emotions in order to compensate for a lack of any strong factual evidence. There isn’t strong factual evidence that this policy really works in reducing road death and injury but it’s being rolled out authority by authority using salami tactics to minimise the level of dissent at any one time to fit a hard left paternalistic agenda. Doing it ward by ward removes the bigger issues of the traffic flow over London as a whole from public view. It is top class cynical politics. Still what does it matter to Labour what people who work think of it all? Nothing. And that’ll be why they’re losing elections …

          • Anthony Miller

            The whole of London is not one big traffic jam it depends where you go and when you go particularly in Croydon which is on the edge of the urban sprawl. For example you can drive from Fairfield Halls to Selsdon Sainsburys out of rush hour pretty much 30mph all the way and there are only two sets of traffic lights. Saying the words traffic and jam over and over again and parroting the average speed for driving in the whole of London does not make this less true. It just is so. Although it raises the question if you could control all traffic flow using traffic lights down to 20mph why do we need to put up signs at all? To which the answer is probably either that you can’t or that that’s not the real aim of the policy.

  • ScaredAmoeba

    “I was able to find in the published literature, the 6% reduction in accidents per 1 mph speed reduction”
    Source: Taylor, M. C., Lynam, D. A. and Baruya, A. (2000), TRL Report 421 – The Effects of Drivers’ Speed on the Frequency of Road Accidents. Crowthorne: TRL