DfT expects drivers to be familiar with metres and that’s official

Ronnie Cohen reports on his recent correspondence with the UK Department for Transport (DfT).

I recently asked the DfT what measurement units they expect drivers on British roads to be familiar with. It responded (ref. GT51/2/2/F0014554), saying “The answer to your question is that we would expect drivers, for the task of driving on British roads, to be familiar with miles, yards, feet, inches, metres and tonnes.” (my emphasis). I also asked it to supply me with any relevant documentation about what drivers are expected to know about measurement units, especially the ones that appear on traffic signs, and was told that this information can be found in the Highway Code and Know Your Traffic Signs and that both can be accessed from the following link:


What a contrast this is to the claim that drivers who have not received metric education at school would be confused by a change to metric units (Parliamentary Written Answer, 11 July 2002, Hansard, Col 1116w). In a previous Metric Views article, I asked the DfT what evidence it had for this claim and it admitted that it had none (see http://metricviews.org.uk/2013/05/dft-guilty-of-making-unfounded-claims/).

Metres are used throughout The Official Highway Code, sometimes on their own. For example, the 2015 edition of the Highway Code, an official DfT publication, states on page 29, “You MUST be able to read a vehicle number plate, in good daylight, from a distance of 20 metres (or 20.5 metres where the old style number plate is used).”. Metres appear on their own in other places in the 2015 edition of the Highway Code:

  • Page 32 shows a table with an entry for a “child from 3rd birthday up to 1.35 metres in height”.
  • Page 40 of the Highway Code shows a table on speed limits with an entry for “buses, coaches and minibuses (not exceeding 12 metres in overall length)”.
  • Page 42 tells drivers, “If you have to stop in a tunnel, leave at least a 5-metre gap between you and the vehicle in front.”.
  • Page 101 tells drivers, “Tramway overhead wires are normally 5.8 metres above any carriageway, but can be lower.” and “Where overhead wires are set lower than 5.8 metres, these will be indicated by height clearance markings – similar to ‘low bridge’ signs.”.
  • Page 117 contains a couple of sentences with metres only. Under the heading “Large goods vehicle rear markings”, it states, “The vertical markings are also required to be fitted to builders’ skips placed in the road, commercial vehicles or combinations longer than 13 metres (optional on combinations between 11 and 13 metres)”. Under the heading “Projection markers”, it states, “Both required when load or equipment (eg crane jib) overhangs front or rear by more than two metres.”.

Metres also appear on their own in a few places in Know Your Traffic Signs:

  • Page 87 tells drivers, “Marker posts, located at the back of the hard shoulder at 100 metre intervals, show the direction to the nearest telephone (housed in an orange box).”
  • Page 88 tells drivers, “Some motorways may have special chevron markings in the centre of traffic lanes. These are spaced 40 metres apart, …”
  • Page 127 tells drivers, “Drivers should stop at the broken ‘give way’ line (about 1 metre before the crossing) when pedestrians are using the crossing.”

Despite the fact that the DfT expects drivers to be familiar with metres, as we can clearly see in the Highway Code and in Know Your Traffic Signs, they have never allowed distance signs to display metres. Since 1981, the DfT have allowed metres to be displayed on vehicle dimension signs but only alongside feet and inches, never without the imperial conversion.

So why are the Government and the DfT so opposed to the use of metres on distance signs and why do they still insist that vehicle dimension signs must display feet and inches when metres would be enough? Why is there a disconnection between the measurement units that appear in official DfT publications and the measurement units that appear on official road signs? The fact that they do not even allow distances to be expressed in metres in the Traffic Signs Regulations and General Directions 2016 surely has nothing to do with cost. The use of yards for distance signs could be phased out over several years and replaced with ones showing metres when the signs are due to be replaced with no additional public expenditure. Alas, the political will to do so is absent. The UK is virtually unique in the whole world for not allowing metric units on almost any road signs. This is unlike the USA, the only other major country that uses non-metric road signs, which allows them as an alternative.

Successive governments and the DfT apparently have had an unwritten policy for many years of using metric units for professionals and imperial units for general road users on British roads. An example of this can be seen with its instructions to road contractors to place road works signs at intervals of 100 metres but display the signs in multiples of 100 yards. How illogical is that? Only the DfT insists on such nonsense. Yet, the DfT expects drivers to be familiar with both systems of measurement in the Highway Code!

11 thoughts on “DfT expects drivers to be familiar with metres and that’s official”

  1. Unfortunately, the government is engaging in pure political theatre.

    One can only hope that the next government, if Labour takes the helm at Westminster, will see the light and convert road signs and direct the BBC to drop Imperial altogether.


  2. I’m not sure to say that the DfT is “opposed” to the completion of metrication, in the sense that they have an ideological opposition, any more. But consider, if you were in the shoes of a senior DfT official intent on completing metrication, given how needlessly politicised measurement units have become in the UK, how you might proceed? Were it I, I’d proceed in gentle steps, so as not to wake the baby. I’d imagine within the next few years, possibly under cover of some post-Brexit legislation changes, that metres at least, and possibly km would become permitted on signage on an equal basis.

    With the two measurements in free competition, councils would make the decision, as ever, based on keeping costs down. They’ll all see which way the wind is blowing, and there would only be one winner, the one that won’t cost lots to replace all at once when legislation shifts to mandatory metric.


  3. If drivers have to know metres, then by definition, they will also know kilometres.

    As has been said ad infinitum, conversion of our road signs to the world’s measurement system is long overdue. Imperial units in 2017 and beyond make this country more of a laughing stock in the eyes of the world than it already is.


  4. When you speak the DfT again, I would like for you to ask them why is metric prohibited on signs? If someone or a community wants to have metric on road signs, why is it illegal. Then ask them why they allow vandals to alter signs?

    It might help if the person you are talking with can refer you to a higher up that you can speak with personally about changing the rule prohibiting metric to allowing it and for them to prosecute vandals that damage signs by altering them.


  5. Another very good article from Ronnie Cohen
    Readers may also wish to look at the Gibraltar Highway Code, this gives us a good idea of what a metric Highway Code may look like ( Not perfect as they have used Tons although this could just be a mistake).
    If Gibraltar can move with the times why can’t the UK ?


  6. Has anyone tried to contest a speeding conviction in UK on the grounds that “mph” is gibberish?
    m is the abbreviation for metre, not miles. mi is the abbreviation for miles.
    p is the abbreviation for several terms in physics and chemistry, but “per” is not one of them.
    h is the abbreviation for Planck constant, among other things. hr is the abbreviation for hour.
    So a good old British muddle. Chaos? It can’t be chaos, for to have chaos you must first have order.


  7. @jackthesmilingblack

    Actually, h is the symbol (not abbreviation) of hour, not hr as you suggest. Which is why you see km/h.

    I agree with your other points, and mph should really be shown as mi/h.


  8. @jackthesmilingblack:

    ISO 31-1:1992 Annex A (‘The use of these units is deprecated’) says the symbol, as opposed to abbreviation or acronym, for imperial miles is ‘mile’ (also mile², mile/h, etc.). No ‘mi’ for that one, possibly because it’s only an unfortunately placed bolt head or bird poo away from being mixed up with millilitres! USA FHWA, take note. Other highlights include ‘ft’ & ‘in’ rather than ‘’ & ‘″’ and ‘yd’ rather than ‘yds’. In UK, we are not confused by all the different types of ‘m’ on the road signs because of the spacing, or something 🤔.

    We’ve already been through the ‘h’, ‘h’ and ‘hr’ one with you before.


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