Progress at last on vehicle dimension signs

The 2016 traffic sign regulations banning new imperial-only vehicle dimension signs were laid before Parliament on 23 March 2016 and came into force on 22 April. Ronnie Cohen looks at the chequered history of this commonsense reform.

The replacement of imperial-only height and width restriction signs over a four-year period was proposed but not implemented by the last Labour government. The proposals were dropped in 2010 by the incoming coalition, which boasted of the resulting savings but omitted to mention the estimated overall increase in cost due to the disruption and expense resulting from accidents. Earlier posts on Metric Views describe this in more detail.

The proposal reappeared in slightly different form towards the end of the life of the coalition government, and again was not implemented before a general election intervened.

Finally, in November 2015  the Department for Transport (DfT) published a further consultation. Among wide-ranging proposed revisions to the Traffic Signs Regulations and General Directions (TSRGD), the DfT proposed that new signs indicating height, width and length limits should show both imperial and metric units of measurement. One of the questions asked in the consultation was “Do you agree that we should only prescribe dual unit (imperial and metric) height, width and length limit signs?”

This proposal to make metric units mandatory for such signs (in addition to imperial units) was supported almost unanimously by local authorities –  96% of local authorities and 88% of all respondents were in favour.

From 22 April, newly-erected imperial-only height and width restriction signs are unauthorised, unless they have planning permission. Unlike some of our opponents, we do not suggest that readers should take the law into their own hands. However, you may wish to draw the attention of the responsible authority to the relevant section of the TSRGD 2016.

UKMA would, of course, have preferred a rapid move to metric-only signs, including those for speed and distance. While the government’s proposal will result in further wasted expense before the inevitable conversion of all UK road traffic signs to the world standard system of measurement system, UKMA believes it is  an important step in the right direction.

The government recognised in the consultation that “there are a number of lorry drivers on our roads who may not be familiar with imperial units of measurement, particularly younger drivers who may not have been taught imperial measurements at school” and that “this lack of understanding has been implicated in incidents of bridges being struck by over height vehicles.”

Existing imperial-only signs can remain in place until they become life-expired or replaced during routine maintenance. When they are replaced, the dual-unit equivalent sign will have to be used. Existing signs may remain, but will need to be replaced with dual signs at the end of their life, or if renewed for any other reason.

It may be opportune to mention UKMA’s recent report on vehicle dimension signs, prepared following inquiries to highways agencies and local authorities and entitled: “Vehicle dimension signs in the UK: A review of current practice, and opportunities for improvement“.

You can find the 2015 traffic signs consultation at:

You can find the “Traffic Signs Regulations and General Directions 2016” at:

You can find details of the 2006 UKMA report on changeover of all UK road traffic signs at:

We shall be returning to the issue of road traffic signs in future posts on Metric Views.

23 thoughts on “Progress at last on vehicle dimension signs”

  1. Now that the UKMA has its foot in the door, the next step is to push for inclusion of metric on all signs.

    I hope in future postings, supporters can post pictures of new signs that they have encountered in their neighbourhoods.


  2. I would look very closely at this proposal. In response to the unequivocal evidence about bridge strikes, the DFT has made the absolutely minimal response that they could get away with.

    * The signs will have dual measurements, which means that the signs will be cluttered and harder to read.

    * Bridge strikes will therefore still be higher than they need be.

    * Dual signs will make it easy for people to ignore the metric measures.

    * The signs will be phased in over goodness knows how many decades it takes the old signs to wear out.

    * Until all the old signs are gone, the older measures will be effectively the primary measure, because the metric measures will only be on the newer signs.

    I think it’s a delaying tactic from a department that is notorious for resisting metrication. Despite all this, however, it is another sign of creeping metrication in the UK.


  3. @Michael Glass 2016-04-26 at 01:01

    You wrote: “the unequivocal evidence about bridge strikes”. Have you seen something we haven’t? All we saw was data showing that foreign lorries also hit bridges in the UK. What we didn’t see was any evidence that they were more likely to hit a bridge in the UK than they were in their own countries, or any causal link to road signs. Remember, correlation does not imply causation.


  4. Michael,

    I see the exact opposite happening. Look at these signs:

    1.) The metric numbers are on top and in slightly larger font than imperial. They are more likely to draw attention to themselves.

    2.) The metric opposition is opposed to dual signs for the opposite reason you mention. To them, because of the point made in 1.) above, the population will relate to the metric that they learned in school and start to ignore the imperial.

    3.) The signs may not take that long to phase in. Allowing a time for the sign to wear out prevents whining and open resistance if a cut-off date is set-up. Dual signs were already the norm on some roads before the law went into effect and there is no reason to think that, except in some rare cases, the speed of the change won’t happen quickly.

    4.) The old measures are not the primary measures. The primary measures are on the top and those are the metric measures. Those are the units the work crews actually measure in. The units on the bottom are just the afterthought.

    The DfT was run by an anti-metric manager (Hammond). He would have never even allowed dual signs. The new manager I believe is pro-metric, but has to tread lightly. The dual height/width signs are a test to see if he can carry it to the next step without ruffling too many feathers. Don’t be surprised if the next change will allow for dual metric distance and speed signs. Once metric is present and the people are adjusted to it, then a removal of imperial will be the final step.

    It is unfortunate that baby steps have to be taken, but we have to accept that for now.


  5. Daniel,

    I stand corrected. The metric dimensions are on top and in a slightly larger font than the imperial measures. That is all to the good. However, the fact that some signs are changed does not automatically mean that distance and speed limit signs will be changed or even that this is a steppingstone to further changes.

    Charlie P

    Here is the evidence you asked for.

    Note this passage:

    “The Department of Transport said that more than ten per cent of ‘bridge strikes’ involved foreign drivers – who had tried and failed to squeeze under them.
    Imperial road signs are being blamed for the problem as just 0.4 per cent of all vehicles – and just over three per cent of heavy goods traffic – on Britain’s roads are registered abroad.

    “Network Rail has pleaded with ministers to replace signs which show yards, feet and inches to cut down on the cost of repairing the bridges.”

    So just over 3% of lorries are causing 10% of the bridge strikes. Foreign lorries are at least three times more likely to hit bridges than UK lorries. No wonder Network Rail pleaded for the change in signs.

    Charlie, questioning metrication might slow its pace, but creeping or galloping, the change to metric measures continues.


  6. Charlie P wrote: ‘What we didn’t see was any evidence that they were more likely to hit a bridge in the UK than they were in their own countries’

    This is a quotation from the first link in the above article: ‘Based on records from Network Rail’s incident logs since April 2008, approximately 10 – 12% of bridge strikes involved foreign lorries. This is disproportionately high in terms of the number of foreign lorries on the road network.’

    This is evidence enough, isn’t it? While it does not state explicity that the road signs, or the lack of understanding of imperial units on them, is the direct cause of the strike, that information would be recorded, if given, in the statement made to the police, which would not be in the public domain. It would enter the public domain if a driver were prosecuted and he put forward the imperial units as part of his defence for hitting the bridge. So to find that evidence you will have to trawl through court reports or media accounts of court proceedings. I wonder if a foreign driver with little or no English who had put a rail link out of action by hitting a bridge and caused extensive damage to the road (one road had to be resurfaced at a cost of £100 000 to the council) would be strong enough to stand up and state that it was the incomprehensible units of measurement that flummoxed him. I am sure the driver would just as easily claim that there was no sign there – at least not one which he could recognise and understand as such. You underestimate what a problem this is. There may not be as extensive documentation (‘evidence’) to back up the argument as you would like to see, but I have spoken to drivers and been told they are confused by the lack of clear metric information which they find everywhere else they drive in and around Europe (though probably not a number that would constitute ‘conclusive evidence’ for you). At least we should hopefully see fewer bridge strikes with dual measurement signs, but they do seem to take longer to look at and see the information you are actually looking for. Another factor is that many bridges are old and thus rounder and lower than they would be if built today – another reason for using the clearest signage possible to indicate the clearance available.


  7. @Michael Glass 2016-04-29 at 03:08
    @Jake 2016-04-29 at 10:42

    The only evidence you provide is that a bigger percentage of foreign drivers than British drivers collide with low bridges. I think you will also find, if you look, that a bigger percentage of foreign drivers than British drivers collide with everything. That could be because: foreign drivers may not be so well trained as British drivers, they may be more careless than Brits, they may have less respect for the rule of law than Brits, or for any one of a list of other reasons. We haven’t seen evidence that it is because of our road signs (no, the use of the excuse “I didn’t understand the sign” is not evidence). What we need to be able claim that British road signs are the cause is evidence that rules out all of these other possible causes.

    Given that British drivers have one of the best road safety records in Europe and that drivers from countries in eastern Europe have amongst the worse, I suspect you will find that their collision rate when driving in the UK is significantly worse than their UK counterparts just as it is when they are driving in their own countries. Or do you have evidence to the contrary?


  8. Now that I’ve read the old 2009 article in the Daily Mail (thanks to Michael Glass), I note this paragraph:

    “Network Rail has pleaded with ministers to replace signs which show yards, feet and inches to cut down on the cost of repairing the bridges”.

    My goodness! If Network Rail could not persuade DfT to put up metric height restriction signs, there must be anti-metric conspiracy afoot in the DfT.

    And Derek Clark of UKIP was quoted at the time as saying:

    “[This] is all part of the EU’s ploy of drawing us into the continental mindset.”

    What on earth is the “continental mindset”? It also completely ignores the fact that SI is a world-wide system of units, not just a European one.

    Let’s hope clearer thinking steers the DfT in the next government and Imperial finally gets tossed into the dustbin of history. (Maybe such a move will also inspire the right folks here in the USA to follow Britain’s lead and metricate my own country at long last!)


  9. There is also the argument that the British Government is terrified of prosecuting because the courts might rule that the use of the single and double apostrophe to denote feet and inches is contrary to the EU derogation (EEC/181/80) permitting feet and inches to be used provided that the symbols “ft” and “in” are used. As I understand it, the degrogation was based on provisions in ISO 31. If the courts made such a ruling, the Government would have to fund an immediate replacement of all road signs concerned (as well as having considerable egg on its collective face).


  10. Charlie P wrote. ‘I think you will also find, if you look, that a bigger percentage of foreign drivers than British drivers collide with everything. ‘

    Where’s the evidence?


  11. @Martin Vlietstra 2016-05-02 at 06:10
    You wrote: “There is also the argument that the British Government is terrified of prosecuting “. Where is this argument documented or discussed?


  12. @Michael Glass 2016-05-03 at 05:08

    There was no evidence in that guide you pointed to showing that foreign drivers hit bridges because of signage, or lack thereof. And although Network Rail is a state owned company, this is not an official government report or scientific analysis of bridge strike statistics (which is what we need to support your claims), merely a good practice guide for haulage company consumption. You’ll need to try harder than that to convince the non-partisan amongst us that there is any credibility in your, so far unfounded, claims relating to the causes of bridge strikes.

    @Jake 2016-05-03 at 10:00
    For a comparison of road accident stats between UK and eastern European nations see:

    It states: “Sweden, the Netherlands, the UK and Malta have the lowest reported road fatality rate, below 30 dead per million inhabitants.” whilst “The highest road fatality rates are reported from Latvia, Romania, Bulgaria, Lithuania and Poland with more than 80 dead per million inhabitants.”

    Take a look at all the tables and diagrams too, and you’ll soon see the evidence supporting my statement.


  13. Charlie P seems to be upset by the argument used that foreign drivers hit bridges more often than UK citizens has resulted in having metric added to height/width signs. Does it really matter? It is an argument that worked to secure the addition of metric units to signs that are visible to the masses and exposes metric units to every driver.

    It will also prove to all that metric on road signs is not opposed by anyone except metric opposers. This will give support for the addition of metric units on all road signs. We got our foot in the door and that is the best for now we could hope for.

    We must take advantage of this momentum and push for changes in the law not only to allow metric units on all road signs but to eventually require metric to be there.


  14. Charlie P:

    The connection between foreign drivers striking bridges and the lack of metric on height/width signs comes from the drivers themselves. When a driver hits a bridge he is interviewed by police as to why he did not observed posted height restriction signs. The reason often given is the driver did not know what the gibberish on the sign means. At least now with metric required to be on the sign, that excuse will no longer be valid. Now, we need to have the posted sign in the vehicle to be metric too so the driver can compare.


  15. There are four possible categories of warning sign:
    and no sign.
    Similarly, there are four possible categories of in-cab height indications. Thus there are sixteen combinations of sign/indication.

    A randomised trail would let us know the frequency of strikes for each combination.


  16. @Charlie P:

    For someone who claims to be so keen on evidence, there is an awful lot of conjecture, evasion and dissembling in your comment. Perhaps you would care to practice what you preach and furnish us with the particulars in this instance? Be thorough yet concise and assume we’re all sceptical, but open to reason. In the meantime, I’m content to believe that Network Rail and the motor insurance cartel know a thing or three more about bridge crashes and highway signage than you.

    The term `road safety record’ is heavily loaded, highly subjective and quite a big red herring in the context of a comment supposedly about crash rates, with bridges or anything else. All you can really demonstrate is that fewer people, including bystanders, are killed or receive life-changing injuries as a result of motor crashes in some countries than others. This gets us no closer to knowing why that might be, the comparative number of crashes with or without injury and what any of the above has to do with motorists causing extensive damage to bridges labelled only in arc-minutes en-dash/ minus arc-seconds on almost-but-not-quite Vienna Convention signs.


  17. @ Charlie P

    I am familiar with the report by the European Commission to which you draw attention. However, the document mainly concerns fatalities; it has nothing to do with bridge strikes. I am quite aware that some eastern European countries have a poor record in this regard (as do some western European countries). A driver from anywhere outside the UK who is faced with a bridge height sign still only showing feet and inches will generally not be able to judge whether his vehicle will pass through unless he has gained experience of driving in the UK and knows how to convert his vehicle height to feet and inches. There is no arguing with this. As it is often difficult to reverse an HGV safely without assistance, especially if the vehicle is left-hand drive, a driver may well try his luck, especially if he is on the route he has been told to drive. It is not always possible to provide clinically-tested, irrefutable government proof of every kind of dangerous situation. Sometimes years go by, many accidents happen and people are killed before an official report is commissioned. Sometimes you have to rely on common sense and a skilled assessment of the situation to determine the likely causes.


  18. Charlie,

    The Daily Mail article shows that both the Department for Transport and Network Rail pleaded for the change in signage. This isn’t my doing but is the work of the Department for Transport and the UK Government. My second reference said,

    “A survey in 2011 indicated that drivers believed causes of bridge strikes include…
    • Drivers not understanding signs (15%)…….
    • Inadequate signing (9%)”

    2011 is five years ago, so the decision for dual signs hasn’t exactly been rushed. The decision has now been made, and the changes are being implemented, so complaints about this change will not put the clock back.


  19. @Mark Williams 2016-05-08 at 14:29

    You appear to be asking me to prove beyond reasonable that the unfounded speculation about road signs might possibly be wrong.

    Perhaps you should instead be asking those who are making the irrational claims that one particular correlation implies causality to provide evidence and reasoning that rules out all of the many other correlations as potentially causal.


  20. @Charlie P:

    No, I’m merely asking you to prove (balance of probabilities would do) that your unsupported claims are definitely true and not just stuff which you made up.

    Your dodging of the other points raised in the comments—including, but not limited to, mine—is noted. It hardly seems worth the bother of starting to unpick your [quite separate] attempt to absolve the gobbledegook signage of any blame while you are determined to remain so slippery! However: I am shocked that such a renowned logician as yourself could make such an elemental error…


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