DfT prefers imperial units to pedestrian safety

Signs indicating the emergency escape routes in tunnels are of critical importance to the safety of tunnel users, given the particular hazards of fire and smoke within tunnel environments. Sadly, the government’s irrational position on units of measure even extends to these safety critical signs, as illustrated by the different units being used by the same authority on adjacent tunnels.

By international agreement under the auspices of the United Nations, new road signs showing pedestrian escape routes with distances were adopted for international use in tunnels in 2003, providing a common design for use in all countries to improve evacuation in the event of a tunnel incident. These new signs added the distance in metres to the nearest exit, as illustrated in the updated Vienna Convention on Road Signs and Signals:

pedestrian escape signs G24

In the UK, the Department for Transport (DfT) noted this advance, but decided that new signs using obsolete imperial units should be erected in tunnels across the UK, regardless of whether young people or visitors to this country may need to be evacuated from a tunnel, and heedless of government guidance that metric units are the primary system of units in the UK.

New signs are being installed by highway authorities in tunnels across the UK, including in London, where Transport for London (TfL) are refurbishing road tunnels with new signs showing the distance only in yards (and to the nearest yard!), as shown in this picture taken in the Rotherhithe Tunnel:

Pedestrian escape signs imperial

Meanwhile, TfL re-opened the refurbished East London line last month, whose tunnels pass below the Rotherhithe road tunnel.

This being the UK, the same standards do not apply in road and rail tunnels. New escape signs have also been installed by TfL within the rail tunnel adjoining the road tunnel:

Pedestrian escape signs TfL

Unlike the road tunnel, the rail tunnel is signed in metres, meaning any visitors are able to judge the distance to the emergency escape. Full marks to the rail authorities for using units all potential users will understand, but it highlights the mess that the UK is in when adjacent tunnels, one road and one rail, under control of the same authority, provide critical passenger safety information in different units and expect users to be able to understand both.

Sadly, other backward steps have been made within the rail tunnel. Line distances on the London Underground network changed to kilometres as long ago as 1972, but with the conversion of the East London line to National Rail standards, new mile and chain marker posts have replaced the metric signs which have stood for nearly 40 years. The new yellow sign below indicates the 3 ¾ mile mark:

Pedestrian escape signs Network Rail

At least these signs are not for public consumption!

34 thoughts on “DfT prefers imperial units to pedestrian safety”

  1. So, does this mean such signs posted in Wales will be bilingual English/Welsh? These will be even more helpful to visitors from outside the UK when they’re in bit of a panic looking for the escape route, I suppose.

    Is there cause for asking some agency in the EU to look into this? It seems there are ground for questioning the posting of signs in this way.


  2. The sign showing 1568 yards looks quite ridiculous. They couldn’t be more unhelpful if they tried. The imperial minded pedestrian is unlikely to have much idea how far such a distance is in terms of walking (or running) time. On that scale they think in miles and given the general lack of knowledge (nowadays) of the number of yards in a mile many will find it difficult to convert (not that it is all that easy even if they do know).

    If it had shown 1433 m then metric aware pedestrians would at least be able to assimilate it as about 1.4 km. That of course is the beauty of the metric system – scaling is so easy.

    I find it quite disconcerting that people entrusted with the task of providing public information seem to have no idea how to handle measurement.


  3. Why not write to your MP and ask him or her to ask the Secretary of State for Transport why the DfT are giving such scant regard to international safety standards?

    If these signs are being classed as road signs, then they are even disregarding their own rules on the rounding of distances.

    For most distance signs the TSRGD prescribes:
    “distances of less than 1/2 mile being expressed in yards to the nearest 10 yards”
    “distances of 1/2 mile or more but less than 3 miles being expressed to the nearest 1/4 mile with the fractions 3/4, 1/2 and 1/4 being used”

    Trying to involve the EU would only give the DfT support from the tabloids. Besides which the EU have made it perfectly clear that it is up to the UK government to decide when to abandon the use of second rate measurement units on our road signs.


  4. One other area of confusion is the fact that in many cases signs marked as yards are really metres in disguise. Can this also apply here? Is it 1568 yards (1433 m) or is it 1568 m to the exit? The difference is 135 m.

    Who would know for sure what is the true meaning in the numbers?


  5. Isn’t this sheer madness? I’m 43 and never used a yard in my life. Even in 25 years in department store retail, with fabric, carpets, curtains, blinds and other drapery very much a part of my everyday work. At school, we ran the 100m, 200m, 400m 800m and 1500m. When I see the countdown markers on the road I don’t think of it as yards, I think of metres. It is just such an outdated and redundant reference.

    Ok – this is time to write to Cameron, Clegg and Hammond! I have also vented my feelings on the ‘yourfreedom’ website where Mr Clegg is asking UK citizens views on what laws we like and dislike. There is a thread there for just eventuality – quoting metres instead of yards on roadside, along with a couple of other imperial v metric debates.


  6. I’ll second what it said by Jeremiah… there are examples in several road-related documents produced by the DfT that actually state that yards and metres are effectively the same that when it’s become unclear what the actual definition of a yard is.

    It is clear in this case that these signs are there for health and safety purposes and not for the direction of traffic so surely the safety aspect should take priority here and hence the signs should, by law, be in metres and not yards.


  7. It looks like these signs have been placed at round multiples of 50 metres from the nearest emergency exit, as per rule 11(b) in section G(V) of the Convention, but that UK sign regulations requiring “yards” to be used on road signs, instead of metres (using the universally understood “m” symbol), means that the values to the nearest exit are shown in multiples of 54.68 yards.

    Still, at least they’ve dropped the decimal fractions of yards – we wouldn’t want the signs to look silly now would we.


  8. Jeremiah & Alex wonder whether the imperial figures given actually refer to metres or to yards.

    According to the sign, the total distance between the exits is (1568 +54) = 1622 yards

    The Wikipedia article on the tunnel gives the length as 4860 feet. That’s equivalent to 1620 yards or 1481 metres


    On this occasion, therefore, it looks like the DfT have actually given the actual yardage instead of their common practice of measuring in metres & presenting the result in yards.

    Why can they not just pick one RATIONAL measurement system and stick with it?


  9. Perhaps someone can explain why road sign regulations would be applicable if these signs don’t apply to vehicular traffic.


  10. A supporter of the imperialist British Weights & Measures Association, writing to the City Corporation in 2009 about a metric pedestrian sign near Tower Bridge, is reported to have concluded:

    “The sign should be … translated into imperial measure. Visitors wish to see Britain, not a hotch potch of their own homes”.

    The fiasco of the road tunnel pedestrian safety signs, not limited to the Rotherhithe Tunnel, suggests that this sentiment, linking imperial signs to national identity, is shared by some at the Department for Transport (DfT).

    This is an example of an insular view of Britain that has become quite seductive in recent decades. ‘Trust the bankers to deal with the global economy, let the revenues from North Sea gas and oil pay the bills, and then dream of thatched cottages’. The government spending review in October is likely to provide a rude awakening. And in an interesting turn of fate, the DfT, a principal culprit of fostering an image of time-warp Britain through its passion for imperial traffic signs, will be among the Departments hardest hit by cuts.

    Visitors wish to see Britain – but safely. And there are also many Britons who have become used to simpler, easier and universal ways of doing things – their safety in tunnels matters too. Their options seem to include hoping for the best, or taking up golf to gain familiarity with these outdated units – the Balgove Course at St Andrews is 1520 yards long.


  11. While my contact in Ireland did not have an opportunity to check if there are similar signs in Irish tunnels, he did assure me that any such signs would have to use ‘metres’ only since Irish legislation explicitly forbids the use of Imperial units on signage (road signs, etc.)

    That’s strikes me as a very poignant reminder of how unfortunate the intransigence of the UK DfT in adopting similar rules is turning out to be!


  12. The continuing problems of distance on British signage seem to come from a combination of lack of understanding of the rules, ignorance about the intelligence of the British public and fears of reprisals from the likes of the BWMA. Over the last weekend I have seen a number of examples that just continue to amaze.

    There is a temporary road sign across the road from my house which reads “CAUTION SITE ENTRANCE 100 METRES” which although not legal seems to have caused no problems in the 6 weeks it has been there, much the same as with as with the signs at a local industrial estate that show distances in metres to various factory units, however there is a height limit sign about 100m before a railway bridge just a few km from me that somebody has vandalised to remove the metric part.

    In London I saw a height limit sign on a cycle path which was metric only, warning cyclists of a road sign across the path which only had a 2m clearance yet many equivalent road signs in the area were imperial only.

    Then on the M1 in Bedfordshire I passed through roadworks, the public side of the cones had width limit signs showing only 6′-6″ but the works side had metric-only height limit signs at bridges and overhead cables.

    While in London I noticed that the “official” pedestrian signs have no measurements at all but have seen some of the ones showing distances in minutes, clearly done to avoid them being vandalised. However businesses such as McDonalds are more than happy to put up signs displaying the number of metres to their nearest shop.

    While there is no clear ruling on pedestrian signs or action against the vandals who de-metricate perfectly legal road signs this mess will just continue to get worse and the chances are that if somebody does get hurt or killed due to this confusion it will be the likes of the tabloid press that will be blaming poor education for people not understanding what a yard is, not blaming the use of imperial where metric is more appropriate!


  13. Head room in Ireland is mostly dual metric and Imperial. For instance at the entrance of the Dublin Port tunnel north of the city on the motorway from Belfast and the airport. I think they want to avoid lawsuits from people who ram their vehicle under a bridge or tunnel that is too low to pass and then claim that they do not understand metric units.


  14. I can understand a claim not to understand imperial as imperial is not taught to any practical degree in any school outside the US. With metric not only taught in the schools almost everywhere but also used in daily life in the markets and on the jobs, such a claim would be with out justification.

    Such a suit would be tossed out of court and the person striking the bridge could easily be found guilty of criminal action if it is proved that they indeed learned metric in school. If they claimed they forgot it then that is their problem and fault.

    It would be interesting if Irish driving tests now require a proof of a working knowledge of metric units. Such a test would deny driving privileges to those that don’t and no license would be given until a satisfactory knowledge of metric units is demonstrated. This would eliminate any need to justify dual unit confusing signs based on such an argument.

    By the same logic, do Irish drivers who speed and cause accidents claim they thought the speed signs mean miles per hour? I remember one case of a speeder getting a light sentence some years ago because even the judge claimed he understood miles better. But wasn’t that travesty put to rest already or is that excuse still used?


  15. Below is a reply (dated 4 August 2010) from Norman Baker MP, the Minister responsible for traffic management, at the Dept for Transport:-

    “By way of background I would first explain the Traffic Signs Regulations and General Directions 2002 (TSRGD) prescribes a sign to direct pedestrians to the emergency exit from a tunnel. However, following the introduction of the Road Tunnel Safety Regulations 2007 which implemented a European Council Directive on minimum safety requirements for tunnels, an additional sign that indicates the shortest escape route has been included in the amendment regulations to TSRGD that we have recently consulted on.

    The distances on this sign are to be shown in yards as the use of metric
    units on traffic signs is controlled by TSRGD; it would be unlawful for any
    highway authority to use metric units in defiance of the Regulations.

    With regard to the positioning of the sign and the unit of measurement used for determining the location, this is entirely a matter for the relevant authority.”


  16. This just goes to show how bad the current rules are… ok, so we have a derogation to allow for imperial measures on road signs but surely this is a clear matter of public safety which, given that these are pedestrian signs, should trump the provisions of TSGRD.

    In addition to this, the clauses in TSGRD banning metric only seem to have been added in recent years with the badly thought out excuse of “avoiding confusion” and there are plenty of places in TSGRD where metric is permitted (or sometimes even required such as for trams) so it can’t be that difficult to make metric permissible on signs intended for pedestrians!


  17. Why on earth would signs directing pedestrians to exits be designated as “traffic” signs. Seems rather odd to me.

    Moreover, metric units are allowed by the TSRGD on signs that announce height, width, and length restrictions. It is simply a matter of amending the TSRGD to permit (at the very least) the use of the symbol “m” for “meters” in addition to the word “yards” on signs in the tunnels.

    A straightforward design would raise the word “yards” above the baseline of the digits to make room for the symbol “m” beneath it. (Other variations are of course possible.)

    The response by Mr. Baker strikes me as fatuous, to say the least. I hope someone on the opposition asks the appropriate question during question time.


  18. The TSRDG does not authorize metric units for distance but neither does it explicitly ban them. It is only those who object to metric indications that claim them to be “unlawful”.

    It is also a tiresome argument to suggest that imperial units are required for British traffic signs in order to comply with European Union directives. The Units of Measurement directive allows imperial on British signs as a concession (derogation). That is not the same as requiring them.

    In any case the TSRGD does not fully comply with that directive, nor for that matter with the UK version, namely the Units of Measurement regulations. The use of ‘m’ for mile (the symbol for metre), ‘T’ for tonne (instead of ‘t’), ‘yds’ for yards (rather than ‘yd’ – unit symbols should not be pluralized) and failure to use ‘ft’ and ‘in’ for feet and inches are all points of departure, none of which are authorized.


  19. Miles and yards work perfectly well, so leave them alone. A huge advantage of the imperial system on roads is distances between moving cars can easilly be calculated. If you stick the ‘2 second’ rule then two cars at 30mph are 30yards apart and at 60mph are 60yards apart. Precise measurements in escape tunnels are the last thing that will be on your mind. Round up to the nearest 1/4 mile and that would be fine. I’ve seen 6′-6″ heights expressed as mm and it just looks rediculous. I think there is better things to spend 700million on thyan uprooting every 100 yard marker and altering it 10yards to be 100m; really does it make that much difference? It’s part of our heritage so leave it alone.


  20. John Gow claims that “A huge advantage of the imperial system on roads is distances between moving cars can easilly be calculated.”

    Leaving aside the fact that there would have to be 1800 yards in a mile for his approximation to be exactly correct, can he please explain this “huge advantage”?

    As far as I can see, it only works if you are exactly 2 seconds behind the car in front, and travelling at exactly the same speed, and even then, it will only tell you that the distance in yards to the car ahead is approximately equal to your speed.

    Personally, all I need to know is that a 2 second gap is the recommended gap to leave to allow me to brake safely. I don’t need to know the exact distance to the car in front.

    If I want to estimate 30 metres, I can do it by eye. It’s roughly half the width of a football pitch (touchline to centre spot) That’s hardly difficult to imagine.


  21. John Gow,

    When you drive on the Continent (or the UK changes), multiply speed limit in kilometers per hour by 0.5 for a 1.8 s gap, or by 0.6 for a 2.16 s gap. I use this when I drive in Canada.

    You could multiply by 5/9 for a perfect 2 s gap, but frankly, there is nothing sacred about 2 s. A little more or less, depending on an individual’s reaction time may be better suited to that individual. Also, most of estimate distance in either yards or meters imperfectly.

    At least in the US, a speed limit in kilometers per hour (few are) must be a multiple of 10, so it is easy enough to multiply. I believe Canada also requires a multiple of 10 (or I haven’t driven on Canadian roads with an odd multiple of 5, but even that is easily multiplied by 0.6)


  22. The 2 second rule is to enable drivers to judge a safe distance by means of timing, not by conversion to distance in yards.

    The 100 yard markers that John Gow refers to are actually spaced at 100 metres.


  23. As an Australian I can assure everyone that using metric or imperial measures makes no difference to road safety. It didn’t even make any difference to road safety when we switched from miles to kilometres. Things like seat belts, random breath testing and other reforms make a difference to road safety.


  24. Thank you for that contribution Michael. It is easy to forget that a number of other countries have made the to transition metric without a problem, including Ireland just 5 years ago. It is only in Britian where we are told that safety and cost are a prohibitive barrier.

    I would suggest however that in Britain there is a gain to be made in terms of safety because of the mess things are in, qv the problem with “bridge strikes” and other hazards and lack of consistent metric signage for height, width and length.

    A complete and decisive change to metric on road signs, coupled with a requirement for vehicles to have an in-cab indication of vehicle dimensions (where appropriate) in metric would eliminate an obvious risk.

    The same could not be said of imperial because it would not solve the problem of continental vehicles on British roads or British vehicles travelling to the continent.


  25. I would add to Phil’s statement about the issue pertaining to continental vehicles on British roads and vice versa that the same will apply increasingly to Irish vehicles on Northern Ireland’s roads and vice versa.


  26. @Len Roberts (Editor: reposted – see below, 2012-07-21 at 20:24)

    Being able to compare one measurement with another requires that they be expressed in the same unit. As you rightly point out the actual unit doesn’t make any difference purely in that context.

    The trouble is that in the UK people are having to cope with different incompatible units for the same type of measurement.


  27. I am grateful to L Roberts for reminding me of this two-year old article in the week that Olympic competitors and officials began to arrive and on the day the UK Department for Transport (DfT) raised the Olympic flag on its HQ.

    These uniquely British signs have recently been installed in tunnels on at least three of the Olympic priority road routes:

    the A102 (the Blackwall Tunnel) between the Olympic Park and the equestrian event centre at Greenwich;
    the A11 and A12 between the Olympic Park and the canoeing centre at Broxbourne;
    the A406 between the Olympic Park and Wembley stadium.

    Readers may be aware of more.

    When will the DfT realise that, while “100 yards” may be understood by many in the UK and by fans of American football, “100 m” is understood, not only in English, but for example in Russian, Greek, Arabic, Mandarin and Japanese?

    Incidentally, the Highway Code provides no advice for those faced by an emergency in a road tunnel. In general, it is best to turn your back on the fire or other incident and head away from it towards the exit, whatever the signs may be telling you.


  28. @Len Roberts

    Now, if the tunnel is full of smoke or dust, would it not be an advantage to know how far to go before starting to look for or feel for the exit? At 100 m most people of the world would be able to translate that into their own paces. Now put that in rods, poles, perches, hands, cubits or whatever you like, then how many paces would you take before stopping to grope for the exit? I can tell you that knowing how far to go before reaching safety is not, in real life, a joke. Also as I live on the coast, knowing how close the cliff edge is in fog or mist can also be usefull, the difference between feet and yards is the difference between life and death. If it is always in one unit that the whole world understands then the chances of error or minimised, and it is life and death chances we are talking about.


  29. L Roberts misses the point of these tunnel emergency signs.

    Knowing the actual distance to the exit is vital information when making a life or death decision of whether to exit a car and make a run for it in a tunnel full of smoke. This is why these signs are specified to show distance as well as direction information.

    On emergency signs, using non-standard distance units that are incomprehensible to the majority of the world’s population is criminally irresponsible.


  30. Just a thought. Let’s pick someone with a low IQ.

    If they saw a sign showing running to the left to right would they not

    1) Go the way the little pic of the man is going or
    2) Go the way that shows a smaller number?

    Fair enough that the unit used is really horrible but I must side with common sense here.

    Which is closer, from A to…..

    B – (26 globits)
    C – (142 globits)

    How long is a globit? Has ‘relevance’ sunk in yet?

    (Editor: this comment is a repost of one first posted on 2012-07-20 at 15:52)


  31. I think BrianAC makes a good point… I recall an experience from my teens that while isn’t entirely safety related does show that units DO make an important difference.

    Having been educated entirely in metric I recall a trip with my local Scout troop for abseiling. We were told by the leaders that the wooden tower we would be using would be a whopping “100 feet tall”. At the age of around 15 I seemed to have little concept of feet for measuring large objects and in my mind I envisaged 100 metres. You can imagine my surprise when I saw a small wooden tower barely even 30 metres in height.

    Apply this to an emergency situation where people are confused and perhaps struggling to breath and you have a recipe for disaster.

    On the same vein despite having driven “thousands of miles” on roads in the USA I still have a brief moment of panic when I see a “lane ends in n feet” sign on the interstates.


  32. @ “Len”

    All you are doing is showing (yet again) why your favoured imperial system is not fit for use.

    BWMA claim that one of imperial’s “advantages” is that units change as numbers get too large to comprehend, and that imperial avoids the need to use 4 or 5 digit numbers to describe measurements.

    This is backed up by The Traffic Signs Regulations and General Directions 2002, which state that distances of ½ mile or more but less than 3 miles should be expressed to the nearest ¼ mile and that distances of less than ½ mile should be expressed in yards to the nearest 10 yards. I understand that you are also an Active Resistance to Metrication supporter, and agree with their interpretation that these regulations apply to pedestrian signs?

    So, in the pictured example, instead of stating 1568 yards and 54 yards, to comply properly with your favoured Imperial requirements, the signs should state “¾ mile” and “50 yards”

    Now, if I understand you correctly, you suggest that the units are irrelevant, and you should follow the sign showing the lower number.

    Last time I looked, ¾ was less than 50.


  33. @Ken

    Rounded to the nearest quarter mile or truncated to the lesser quarter? I make 1568 yd to be 0.891 mi, hence closer to 1 mi. Of course DfT would write it 1m. So comparing 1m to 50yd. That should confuse both Brits and visitors, but rules are rules. I’ll follow the suggestion and go whichever way the “running man” is going. 🙂


  34. Aye John, I probably should have rounded up rather than down, but the confusion just serves to emphasise how innapropriate the Traffic Signs Regulations and General Directions are for pedestrian signage.

    However, if you scroll back up and look at the original picture again, you will find that the running man is attempting to run in both directions at once! A non-imperial user is still left with a guess as to whether 1 “mile” is more than 50 of these “yard” things


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