The 25 percenters

So I have to write a tedious blogpost about the story of a nonsense statistic, a statistic that appears in the Begg report covered in yesterday’s blog post.

Namely, the claim that Mayor Boris Johnson exacerbated the problem of congestion in London

by removing the western extension of the congestion zone and by reducing road capacity in central London by 25% on key routes through the introduction of cycle superhighways [my emphasis]

Elsewhere in the report [p.26] this claim is even wilder –

… by removing the western extension of the congestion zone and by reducing road capacity in central London by 25% through the introduction of cycle superhighways 

I’m not even going to bother with that one, because it’s so plainly ludicrous (at best only 3% of roads in central London have protected cycleways) and because it is most likely the result of a mistaken omission of ‘on key routes’.

But even the former claim is mysterious. Given that there are effectively just a handful of new superhighways in central London – CS5, CS6, CS3 and parts of CS2, how on earth has a figure of ‘reducing road capacity in central London on key routes by 25%’ been arrived at?

Charitably, we might interpret the claim as being a reduction in capacity on some key routes in central London by 25%. (This is an explanation some of those who have disseminated the statistic are desperately falling back on). But if that was the claim that was being made, why isn’t the word ‘some’ actually included, anywhere in the report where this claim is repeatedly made?

Further, in the context of the passage, the implication is quite clear – road capacity has been reduced on key routes by (allegedly) 25% overall, enough to justify comment. To put this another way, if road capacity had been reduced on just a handful of main roads, why on earth would that merit comment in a passage about London-wide congestion? This attempt at an explanation is incoherent.

We then come to the problem of ‘key routes’ themselves. Funnily enough TfL were careful to avoid ‘key routes’ for buses as much as possible when they build the E-W and N-S Superhighways, as you can see from this map of key bus routes, spotted by Jono Kenyon.

Screen Shot 2016-06-14 at 16.18.07

These high-profile interventions barely co-exist with these key bus routes, using routes where there is relatively little (or no) TfL bus activity. If there has been a reduction of 25% on ‘key routes’ it isn’t the ones buses are using. The Embankment, which has seen a reduction in the number of motor traffic lanes (a very different thing from capacity) from 4 to 3 (a potential source for a ‘25%’ claim) is very much not a key route for buses.

So where did this dubious statistic even come from in the first place? The answer (thanks to some digging by Carlton Reid and Peter Walker) appears to be from a Transport for London presentation made by Helen Cansick to the London Travel Watch board, on May the 12th last year.

… the 25 percent statistic is not as robust as it was portrayed in the bus report. For a start, it’s not from a written source. Professor Begg told BikeBiz:

“The statistic comes from Transport for London. Helen Canswick of TfL network management gave a presentation to London TravelWatch at which she was asked what the reduction traffic capacity would be as a result of roads modernisation. She told members they had modelled a reduction of network capacity in the central area of 25 percent.”

Extraordinarily Begg himself confirms here that “the statistic” is actually about reduction in capacity due to the road modernisation programmea programme that encompasses improvements for cycling, but also public realm schemes and improvements for walking and public transport – and, err, road schemes.

This much is plain when we look at the minutes of the meeting during which the Canswick presentation was made.

The Policy Officer asked what the total reduction in road capacity would be under the modernisation plan. Ms Cansick said that following completion in December 2016 there would be a reduction of road capacity for motor vehicles of 25% within the inner ring road.

Exactly the same statistic that Begg says he used (albeit erroneously). Who might this Policy Officer be?

Vincent Stops is of course a London TravelWatch policy officer, one who was present at that meeting, and clearly the person who passed the ‘25%’ statistic on to Professor Begg.

The only remaining question is at what point a figure about 25% reduction due to TfL’s overall road modernisation programme became converted into a 25% reduction due specifically to cycling infrastructure, as the claim appeared in Begg’s report.


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18 Responses to The 25 percenters

  1. AD says:

    It’s also morphed from “a reduction of road capacity for motor vehicles” to “reducing road capacity”, as if non-motor vehicles aren’t part of any road capacity calculation.

    • HivemindX says:

      This is an excellent point. I’m given to understand, by people like the AA and Michael O’Leary, that cyclists are a primary cause of congestion in cities. They look out at the sea of cars and think that, somewhere, a cyclist is causing the congestion. Surely taking cyclists off the road is INCREASING capacity no?

      Even if we don’t believe the theory that cyclists cause a disproportionate amount of congestion surely the loss of one lane out of four for motorists to provide an off-road provision for cyclists will improve the capacity of the remaining three lanes by some percentage, right?

      Anti-cyclist campaigners cannot have it both ways. On the one hand cyclists increase congestion and slow down traffic (in a dire way apparently). On the other hand removing cyclists from a road does nothing to increase capacity. How can both of those things be true?

  2. Simon says:

    Seems like a perfect example of someone coming to the argument with preconceived ideas, half listening to what was said, and concluding that it supports his preconceptions.

  3. Clive Durdle says:

    Actually even if 25% were true it is nowhere near enough! 100% 0n the majority of roads!

    “The first well documented practical applications of traffic calming were the Dutch ‘Woonerven’ designed during the late 1960’s and early 1970’s.

    The early Woonerf streets abandoned the traditional division between carriageway and pavement.

    One surface was created, for use by all road users, and motor vehicle speed was restricted to walking pace.

    Traffic calming was initially applied primarily to residential areas, but is now starting to be extended to whole cities. In the widest sense, traffic calming can be defined as an overall transport policy which includes, apart from a reduction of the average motor vehicle speed in built up areas, design features to encourage walking, cycling, and the use of public transport.

    It can also be defined more narrowly, as a policy to reduce motor vehicle speeds to about 20 mph in urban areas. The street environment and design requires improvement with the objectives of: (a) reduction in the severity and number of accidents in built up areas; (b) reduction on air and noise pollution; (c) increasing the use of non-motorised forms of transport. Examples of traffic calming are given from several towns in West Germany.
    Corporate Authors:
    Friends of the Earth
    26-28 Underwood Street
    London England


    Interestingly, the concept of shared space has been corrupted. Traffic moving at walking pace?

  4. Clive Durdle says:

    As has the concept of traffic calming. “twenty’s plenty” and road humps of various configurations is not traffic moving at walking pace and zero non local traffic.

  5. livinginabox says:

    The claim “by removing the western extension of the congestion zone and by reducing road capacity in central London by 25% on key routes through the introduction of cycle superhighways” Would seem to be little more than nonsense.
    It has to be said that according to Botma & Papendrecht 1991, it would appear that the private car is by some considerable margin, the least effective mode of mass transport. According to Botma & Papendrecht 1991, (assuming representative vehicle occupancy rates) a vehicle lane can accommodate 2,000 people per hour, whereas the same lane given over to cyclists can accommodate 14.000 people on bicycles. I believe a 25% cut i.e. a reduction to 75% is not the same as a 600% increase to 700%. This assumes the same 3.5 m lane width,
    Unfortunately I can’t find the paper for free download. So I haven’t read it.

    • meltdblog says:

      2000vph is only achieved in ideal conditions above 30mph, free flow with just the right amount of traffic. I have a series on flow modelling that includes a look at bicycles:

      • livinginabox says:

        I found the graph on your blog confusing (I’m obviously missing something because there appears to be a need for an additional labelled axis, or a clearer explanation of the graph). The Botma & Papendrecht paper is in persons per hour. Without access to their paper, it’s difficult to know what vehicle occupancy rates were used. In the UK Vehicle (car/van) occupancy (commuting & business, 2013) 1.2ppmv. Single occupancy rate 85%. For 2014 the figures are: 1.2ppmv, SOR 86%.
        Source: NTS0906

    • Tom van Vuren says:

      I found a copy of Botma and Papendrecht here-

      • livinginabox says:

        Tom van Vuren,
        Many thanks for the paper, however, I have completely failed to located within it, the widely disseminated graphic (link below) or any relevant text, that is cited as coming from this document. Furthermore a quck skim failed to identify any relevant connection with the figures cited. Assuming that I am not in error (a dangerous asumption), I suspect that there’s another paper, or some other error has occurred. Perhaps the document was in Dutch and has not been translated?

        Figures cited in graph and attributed to Botma and Papendrecht 1991
        Car 2,000
        Bus 9,000
        Bicycle 14,000
        Pedestrian 19,000
        Tram or train? (uncertain, it’s a graphic) 22,000

        Accompanying text:
        “5 The number of people a 3.5m wide lane can convey with different modes of transport in an hour. The weakest in the comparison is a private car, which only transports about 2,000 people in an hour. As much as 19,000 pedestrians can travel through the lane during an hour.”

        Graphic source

        • AndyR says:

          2,000 people per hour at an average occupancy rate of 1.2 persons/car would roughly equate to a saturation flow of 1,600pcu/hour. Using RR67 (The Prediction of Saturation
          Flows for Road Junctions Controlled by Traffic Signals, Webster and Cobbe, TRL
          , 1966) that is about right for a 3.5m wide lane.
          One assumes the 19,000 peds is based on 7 peds abreast (0.5m of space each) walking at around 1.3m/s (which is pretty fast – think London commuter – older people are down around 0.7-0.9m/s).

        • Jim Moore says:

          I’m pretty sure the figure is from this book
          I often use/post it to make the point that adding non-car paths increase the people-carrying capacity of streets, way more efficiently than adding a lane for motor vehicles.

          IIRC the B&M research only looked at cycle paths up to 2.5m in width for a capacity if 9,000 per hour. Using their methodology for a 3.5m wide path gives the figure of 14,000 in the graphic. The book is well worth a read as it has lots of good examples especially from the NL.

  6. canamsteve says:

    Since you brought it up, I lived in the western expansion of the Congestion Zone while it existed. Its prime purpose, I suspect, was to aggravate the mostly-Tory K&C drivers. The actual effect was to encourage them to drive more, since they got the “resident discount” but it had to be paid for a week at a minimum. For me, this meant to move my car out of London (which I sometimes needed for work) meant that I had “paid” for an entire week of roaming about in the Congestion Zone. It was aggravating as I was only inside it by 500 metres or so and would only move my car to leave. But that’s bureaucracy for you.

    To quote Wikipedia ” It was expected that the extension would increase congestion in the zone by around 5% as the 60,000 residents in the new zone will be entitled to the discounts available.”

    So, if so, one would expect the removal of the Zone to result in 5% *less* traffic (all else being equal).

    Of course, many of my more car-centric neighbours – the ones who drove two blocks to M&S for milk anyway – were thrilled they could drive with abandon into central London again for the price of a cappuccino a week.

    Lies, damned lies and cycling statistics

    • Notak says:

      I’d always thought the CC for residents within it was a yearly thing at a nominal price, kind of like a (heavily discounted) annual season ticket.

      • canamsteve says:

        TBH, I can’t recall if there was a monthly/yearly option for Residents, but it would still have been the 90% discount. As there was no need (for me) to drive in central London, that wasn’t of interest. However, as I did have to drive to some locations outside the city (which using public transport was unrealistic or would require an overnight journey, etc.) it galled me that I had to pay to *leave*. It would have been easy to use the system to record my departure from the Zone (500 metres from home) but as that would add nothing to the coffers, it wasn’t done. Instead *any* appearance on the Panopticon resulted in the charge being levied.

  7. Nick says:

    Agree that the stat is nonsense, but removing capacity on a key route for non-bus traffic can certainly have an impact on the key routes for buses. For instance, if it is more difficult to drive along the Embankment, drivers are more likely to use the Strand, thus making it more difficult for buses to use.

  8. Jitensha Oni says:

    Somehow despite confirming that ‘ “the statistic” is actually about reduction in capacity due to the road modernisation programme’, Begg manages to repeat the (completely unreferenced) 25% in the context you describe 4 times in the report. How is that using a statistic erroneously by accident? Seems like using an erroneous statistic deliberately. Buswash.

  9. colin878 says:

    Hasn’t the road capacity *increased*? The cycleway surely has greater capacity than the ordinary traffic lane it replaced.

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