British drivers face a continuing sign muddle

With the end in prospect for road traffic signs showing imperial-only vehicle dimensions, Ronnie Cohen takes a look at the current muddle.

A Minister of Transport once claimed that “drivers who have not received metric education at school would be confused by a change to metric units on road traffic signs” (Parliamentary Written Answer, 11 July 2002, Hansard, Col 1116w). In a previous MV article (link:, Ronnie Cohen asked the UK Department for Transport (DfT) in a Freedom of Information request what evidence it had for this claim, and it responded that it had none.

New signs showing lengths of vehicles will now be dual: metric and imperial. On the other hand, as a result of politicians’ reluctance over the past 45 years to make the case for metric units on road signs, all distances shown on official traffic signs are in yards, miles and fractions of a mile only. The private sector often takes a different view, and being subject, not to the Traffic Signs Regulations and General Directions (TSRGD) but to Town Planning legislation, shows distances in metres without imperial conversions.

Distances to attractions, restaurants, MOT Centres and other private establishments are just as likely to be given in metres as yards. This use of measurement units reflects general usage rather than government policy.

Distances to car parks are also commonly given in metres:


These metric distance signs are clearly aimed at drivers. Such signs are erected for private sector organisations and are not subject to the TSRGD. They do not count as traffic signs but are classified as advertisements under the Town and Country Planning Act 1990. Under town planning legislation there is no restriction on the measurement units that can be shown on them. Could it be that the private sector, including major supermarkets and oil companies, has more confidence in British drivers’ ability to understand metres than have the politicians?


As discussed in our previous article, new road traffic signs showing vehicle dimensions will always show both metric and imperial dimensions. Yet, oddly, metres appear alone in some places in the Highway Code, and drivers are expected to understand them!

Signs showing a maximum permitted vehicle height on private property are almost always metric. This prompts the question, “Why?”



Private sector distance and maximum height signs for drivers normally use metric units because health and safety legislation requires this. They are widely used and can be found all around us. As a result, drivers face a mix of metric-only, imperial-only (for the moment) and dual vehicle dimension signs. This has led to a large number of designs for road traffic signs showing vehicle dimensions. You can read about the proliferation these in this UKMA report:

The DfT currently uses cost as the principal reason for the failure to convert road traffic signs showing distances to metric. The UK is alone in the world in not permitting metric distances on road traffic signs. The USA uses non-metric measures on traffic signs but allows metric units to be used as an alternative to or alongside imperial units. Surely, it would cost nothing to allow supplementary metric units on signs showing distances and to insist that any new signs or replacement signs use dual units. And it should be possible to achieve this in less than 45 years.

You can find more metric signs at the following link:

25 thoughts on “British drivers face a continuing sign muddle”

  1. All of this disproves the false information put forth my metric opposers that the population prefers imperial and metric only appears by force. Nobody is forcing private users to use metric, they freely choose to do so and their choice is proof the population wants metric.


  2. I’m delighted to see the private sector erecting so many signs in metric. I do wonder how lorry drivers know what the height of their vehicle is in metric if they do not have stickers in the cab showing this information in metric. Or do they?


  3. The last time I hired a large van in the UK (which was many years ago), the vehicle dimensions were printed in metric only behind the sun visor (just as had been the case on the large vehicle I had hired previously from a different vehicle hire company). That was fine by me until two minutes out of the vehicle hire site I came across a low tunnel. With no calculator to whip out and a line of vehicles behind me, I had to resort to winding down the window and visually checking the van would get through the tunnel. The endless bridge strikes in the UK come as no surprise to me, and as a driver I consider the government’s policy stubborn stupidity.


  4. It is a legal requirement in the UK that all UK-registered vehicles that are over three metres in height have a notice telling the driver of the vehicle height in feet and inches. In the case of foreign-registered vehicles, this applies to vehicles that are over four metres in height. I believe that this discrepancy in UK and foreign-registered vehicles is that the minimum guaranteed clearance across Europe is four metres except where individual bridges are marked to the contrary. Various countries can increase this value within their own country – for example in the UK it is 5.03 metres (16 feet) and as a result we can run double-decker busses which are not normally permitted elsewhere in Europe as they are over four metres in height.


  5. @Daniel

    The Facebook page for Active Resistance to Metrication shows a photo of a lorry having hit a bridge even though there were two huge signs in English saying LOW BRIDGE along with what looks like a pretty small sign showing the vertical clearance in both metric and Imperial.

    I wonder if anyone ever sorted out exactly what the driver did or did not do or know or realize before striking the bridge. Root cause analysis would be a good thing!


  6. Of course, some bridge strikes could be prevented by raising the height of a bridge or lowering the roadway underneath it.


  7. The link I intended to post was this one:


    One of the biggest threats to the British way of life is the metric system, or so say the Active Resistance to Metrication We use the Imperial system by law, and yet the sneaky metric system with its sinister metres and kilograms keeps edging its way into public life.

    Luckily, there’s a group of vigilantes that make it their mission to make sure our weights and measures stay in the ever relatable feet, inches and hogshead.

    We sent Jake to spend the day with Tony Bennett – one of the more active members of the movement – to gain an insight into what the actual front line of this war looks like.”

    I noticed in one of the shots, that a legal dual height/width restriction sign had the metric painted out. Metric supporters need to watch for the vandalism of legal metric signs and report them to the authorities.


  8. Martin says: “It is a legal requirement in the UK that all UK-registered vehicles that are over three metres in height have a notice telling the driver of the vehicle height in feet and inches.”

    A notice in the vehicle of a foreign driver in feet and inches defeats the purpose of having metric on height/width restriction signs. As in this photo, a foreign driver struck a bridge with a metric marking:

    Even with the metric marking on the sign he may have not known his vehicles height (even though he should) and may have had to rely on a sign in the cab that he did not understand and could not compare to the posted height on the bridge.

    The Bridge restriction is 4.2 m and since his lorry hit the bridge his vehicle is thus over the 3 m requirement for a posted sign in the cab.

    Even though the words “low bridge” are boldly displayed, there is no indication the driver understood English and those words. The only universal language he would understand are the metric units, both on the sign and in his cab.


  9. @Ezra Steinberg:

    Metric is allowed on the in-cab notices of HGVs (unless the regulation has changed recently). Some have it, others do not. Some do not even have the imperial—there are a lot of motor lorry operators routinely breaking all manner of laws in the UK. How do they understand and manage to adhere to private metric-only height restrictions, regardless? Probably through deep familiarity with the metric system which is used ubiquitously throughout the rest of their work…

    The corollary is: why would an operator need imperial in-cab notices if they were already fully conversant in the arc-minutes and arc-seconds on the road signs?


  10. I checked the video myself and noticed that Tony Bennett changed one sign from metric to Imperial but he left the dual sign alone. This can be seen at 15.02 and following.


  11. Daniel wrote: “Even though the words “low bridge” are boldly displayed, there is no indication the driver understood English and those words. The only universal language he would understand are the metric units, both on the sign and in his cab.”

    This is exactly the point. No one supporting the universal adoption of metric for all public purposes in the UK is trying to eradicate culture, lore or custom. All we are pleading for is the full adoption for public communication purposes of the universal language of measurement – the Esperanto of measurement – which is understandable to everyone from a country that has metric as its primary system of measurement – and that is virtually the whole world, bar the UK and the USA. No country that has carried through its metrication programme to the end has lost its native culture as a result.


  12. It is a legal requirement that metric units should be used for all warning signs that do not appear on roads (for example garage canopies, door clearances etc) with imperial units being an optional extra. On road signs however imperial units were mandatory on the equivalent height and width warning signs with metric units, until recently, an optional extra. At least, by making metric units mandatory on such warning signs, HMG is beginning to see the light. The ridiculous part of insisting on imperial units for such road signs is that all the car owners’ handbooks appear to give only metric units as does Parkers Handbook.


  13. Did Sacha Baron Cohen have anything to do with making this ARM video? Tony Bennett makes Borat and Cohen’s other characters look positively sane. Old Tony should seriously consider getting in touch with Sacha. He could make enough money to keep himself in glue and plastic signs for the rest of his life.


  14. I have an idea to save money on new roadsigns, simply put the 30mph signs in 20mph zone’s then put 50mph signs in 30mph zone’s and so on all you would have to do is put a warning signs to let drivers know it’s a km/h zone and once the public are used to the new speed limits take the warning signs down and recycle.


  15. Not only do drivers on land face a muddle in the UK, pilots in the sky face a similar muddle. This article does a very nice job of laying out the problems with the jumble of different units used in ATC (air traffic control):

    I recommend the entire article. This one part really stands out for me, though:

    “The International Civil Aviation Organization (ICAO) is the governing body that makes official aviation recommendations. It might surprise a lot of pilots that for years, ICAO has recommended that the aviation world move completely to metric units.”

    Just above this quote in the article are two side-by-side photos exemplifying the difference between using metric and using Imperial units. The photo on the left (metric) shows a Boeing Dreamliner; the photo on the right (Imperial) shows a Venator class Star Destroyer of the Galactic Empire fleet. 😉


  16. I am interested to know just how prevalent metric signs are in the UK. Are they common or sporadic? Are metric signs becoming more common or is the ARM’s actions against metric signs effective in mopping them up?

    On 19 January the ARM boasted that they had changed some metric signs on the Houses of Commons. It’s 15 May 2016 as I write. Are the ARM amended signs still in place?


  17. @Michael Glass

    Metric signs are used all over the place by the private sector. Metric height signs at petrol stations and private car parks can be found everywhere with no imperial conversions. Also, distances to car parks are, more often than not, shown exclusively in metres. They can be found in prominent places where thousands of drivers can see them every day. For example, the image in my article with the “MAX HEADROOM” text with 4.5 metre roundels shown on both sides of the text can be found at Wembley Stadium.

    This article shows that the usage of measurement units on British roads has diverged from that elsewhere. The EU PERMITS imperial as well as metric units for UK “road traffic signs, distance and speed measurement”, yet government policy BANS the use of metres for this purpose. Of course, the use of metres for distance on private sector signs aimed at drivers can be found all around the UK. These signs are not classified as road traffic signs and are therefore not subject to government traffic sign regulations.


  18. Ronnie brings up a good point… only here in the UK is the use of metric units on many road signs specifically prohibited, even in the USA metric is permitted and can occasionally be seen – I’ve mentioned before signs on I-5 in California between LA and San Diego where back in 2007 I saw distances shown in “mi” and “km”. I was surprised just a few months ago to see that sign still there, not replaced, not vandalised by some group trying to maintain “Americanism”.

    It really is past time the DfT removed these daft restrictions.


  19. @Cliff:

    So; not necessarily that much money, then? Perhaps it could even stretch to a licence for the Transport Heavy typeface—i.e. the only one authorised in black-on-white TSRGD-compliant signs? Although, one suspects he would still get the x-height(s) and spacing wrong for increased danger/ comic effect :-)!


    Yes, roundel diameter(s) notwithstanding. They could save additional money on advance direction and route confirmation signs by moving them closer to the destinations shown and leaving the numbers unaltered, too ;-). We can also further improve on your suggestion for speeding signs: simply leave the existing roundels exactly where they are when changing from imperial miles per hour to km/h (no smiley, serious proposal)… Who needs Philip Hammond when they have us? By this time next year, DFT could be millionaires!


  20. If the private sector can use metric distance signs (with planning permission) and metric-only dimension signs, why not on official traffic signs too.

    Surely it doesn’t cost anything to amend the TSRGD:
    * Authorise metres and kilometres on distance signs, but ban dual unit distance signs.
    * Authorise once again metric-only vehicle dimension signs, and metric-only in-cab indicators. Imperial-only is already no longer authorised.
    * Ban “m” to abbreviate miles, “m” is the reserved symbol for metres.
    * Require the correct symbols when using metric.

    Of course the literature will need to be updated – namely the Traffic Signs Manual and anything showing sign examples, but this is really not a big cost.

    Ideally the “m” to abbreviate miles should be dealt with first. But in principle, all signs can be replaced at end of life with metric-only versions.

    Given the option of metric signs, I don’t think anyone will use imperial signs when they can use metric signs. I wonder if this would actually be true, if metric-only signs were authorised whilst imperial signs were still in use (and dual-unit signs are banned)?

    And as for speed limits, they will need a cut-off date, and that does incur a one-off cost, but that is it.


  21. “But in principle, all signs can be replaced at end of life with metric-only versions.”

    Not really. Canada and other countries never actually changed signs. They just applied a sticker over the existing sign with a new number. This reduces the cost immensely and you don’t have to wait a long time.

    Vandalised signs should be restored to metric at a cost to the vandals.


  22. Hammond was the Minister for Transport or whatever that over-turned the metric height and width signs in the first place. Don’t expect too much from him, more likely go back the the man with the red flag.


  23. Ezra,

    Philip Hammond is anti-metric. When he ran the DfT he went out of his way to make sure that signs would stay imperial and even resisted dual height/width restriction signs. Now, his successor whose metric views we really don’t know has at least taken the first step. But Hammond’s presence still in government may prevent a full scale metrication of roads or even a partial, by openly allowing metric signs to exit.


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