New speed limit in central London

Ronnie Cohen, one of our regular contributors, comments on the introduction on 2 March of a 20mph speed limit on certain roads in London’s Congestion Charging Zone.

In the Metro newspaper published on Monday 2 March 2020 (Travel News section, page 39), Transport for London (TfL) announced a new 20mph speed limit had been be introduced on the roads it manages in the Congestion Charging zone. The article gave all speeds in miles per hour and all distances in kilometres. Apparently, TfL like many other organisations in the UK sees nothing unusual with mixing two measurement systems in the same article.

The new speed limit involves new signage, road markings, raised pedestrian crossings and re-calibrated speed cameras, publicity and advertising, a new speed enforcement team, new laser video technology and TfL co-operation with boroughs and the public. It is being rolled out across 8.9 km of roads in the Congestion Charging zone. Over the next five years, TfL is planning to introduce safer speed limits across another 140 km of London’s roads.

These measures are intended to make our roads safer and are part of the TfL Vision Zero commitment to eliminate deaths and serious injuries from London’s roads by 2041. Safety measures are to be welcomed. But the introduction of 20mph signs and road markings in recent years is surely a missed opportunity to introduce metric signs. If they had been metric, they would have cost no more than the current imperial versions.

Information on costs and funding did not feature prominently in the news about the CCZ 20mph limit (in contrast to the successive proposals for the conversion of the UK’s road traffic signs to metric measures). The question of whether there would be be extra funding for new signage, etc, or diversion of funds from other parts of the transport budget was left open, but there appeared to be an implicit assumption that the money would be there.

Covid-19 had not made an appearance at the time these plans were being prepared, and the economic consequences of the pandemic could not have been foreseen. We must hope TfL Vision Zero does not take as long to be implemented as the proposals for metric road signs – 50 years and counting!

As well as the printed Metro article, you can find the same story on line at the following links:


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10 Responses to New speed limit in central London

  1. BrianAC says:

    We can now at least state with more certainty that road miles shown in km is a de-facto occurrence.
    This further advances my theory stated elsewhere on these pages that UK now has a de-facto "UKC" (UK Customary) measuring system which will be with us for the rest of our lives.

  2. Daniel Jackson says:

    8.9 km? Why not 9 km?

  3. BrianAC says:

    Daniel, 8.9 km, speculation, but probably because that will be a precision survey measure, not a random estimate.
    Given the value of land in any big city, let alone London, I would guess they know pretty much the road lengths to the millimetre!
    We do have a pretty good metric surveying record in this country, OS is pretty much all metric in its survey work, annoyingly though, not in its leisure book publications which stop me from buying them.

  4. Rob says:

    Why is our Highway Code book nearly all metric when we have medieval distances and speed limits shown on our road signs.
    Mixing up different units of measurement on the highway or in the official Highway Code book and the media does nothing for road safety, it confuses our children and is one reason why our driving test is tricky to pass.
    I stopped being a fossilised Luddite many decades ago and my life has a whole new meaning!

  5. Cliff says:

    I wrote to the UK Department for Transport a few years ago asking why they didn't do something about changing road traffic signage to SI units and they replied that it was solely due to cost. Why is cost not a problem where imperial signs are concerned?

  6. BrianAC says:

    @Cliff, cost is costing.

    I guess the D[a]fT know quite well this cost mantra is just a red herring. Their estimates of converting road signs have been trashed any number of times, it makes no difference to them.
    The cost of official duplicity (in all spheres of UK life) and all it involves must be staggering.
    Given the mixed-muddle errors I alone make as a fully imperial-conversant SI convert makes me wonder how others cope, although I do at least have age as an excuse.
    It is our money they are wasting and us they are hurting. The 18th century UK beckons.

  7. Jake says:


    So the Department for Transport did not reply to you that there was an objection on ideological or any other grounds, and that the problem of conversion was solely one of costs. Well, we know that argument was debunked by UKMA quite a few years ago: distance signs can be replaced over a period of time, overlays can be used, costs can be spread over different budgeting periods, etc. The only thing that needs an 'M' day is the conversion of speed signs to kilometres per hour, but there are excellent precedents in countries like Ireland, Canada and Australia. We seem to be in a stalemate situation: the DfT claims it cannot do it on the grounds of cost, we say it can and have even produced publications setting out how it can be done. It's amazing how quickly the Government can find whole forests of magic money trees when it so wishes, as we are witnessing at the present time when thousands upon thousands of people and businesses are being financially supported during the pandemic, yet cost is cited as the excuse for not implementing an eminently sensible and pragmatic conversion of road signs to the units of measurement taught in schools, SI units, in normal times. What do people in other countries make of this, I wonder?

  8. BrianAC says:


    After this pandemic shutdown eases there should be an incentive for job creation.
    One of the projects could be completing metrication, maybe recruit an army of those who have lost jobs to try to lay this ghost to rest once and for ever.

  9. Alex Bailey says:


    We all know from events in recent years that it’s not the truth that matters, only what the public have read in the tabloids. Therefore if a cost was published in the Sun/Mail/Telegraph (and duplicated on Facebook) then sadly any facts produced after that point in time are irrelevant and will be ignored by the voting public.

    I suspect that we’ll be lucky if there are more than minor changes while the current administration continues.

  10. Daniel Jackson says:

    I don't agree with the cost excuse either. But that aside what could it cost or what harm would be done if the prohibition of metric only signage was lifted and the damage done to metric signs by outlaws was punished?

    If it was announced that local communities could erect metric signage if the wanted to or replace imperial signs with metric ones when the imperial ones wore out the change would happen over just a longer period of time. The Irish did something like that. Speed limit signs changed in 2005 after it was determined most of the distance signs were metric anyway.

    Not even allowing metric only signs speaks for itself that there is an ulterior motive behind the scam and the lies.


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