When were metres prohibited on road signs?

Was there any law against metric road signs before the 1970s? asks Kel

On the M3 today I saw the familiar ‘No hard shoulder for 2000 yards’.It’s clear that it really represents 2000 m, which made me think about the fact that metric is prohibited on our road signs. This does not include height and width restrictions of course and there were signs that gave the lane width (there were roadworks) of 2.0 m and 6′ 6″. Can anyone tell me when metric became prohibited on road signs? I would have thought that there was simply no law on it as there would not have been the need prior to metrication in the 60’s/70’s.

Further to this, when did they become allowed for height and width restrictions (alongside imperial) and when did weight restrictions convert to metric, ie. tonnes on mgw signs?

Perhaps metric was always prohibited or did someone make it so to halt the progress of metrication?

Can somebody supply a short history of how this mess came about?

Author: UK Metric Association

Campaigning for a single, rational system of measurement

7 thoughts on “When were metres prohibited on road signs?”

  1. I can’t find any hard evidence but I did find a couple of old road atlases – those ones with information on road signs in them – one published by Hamlyn in 1985 showed weight limit signs using “tons” whereas the 1993 Readers Digest Drivers Atlas of the British Isles uses “T” instead. Neither has any other indication of metric road signs.

    I’ve seen evidence that “Traffic Signs Regulations 1994” allowed metric units in height, length or width provided feet and inches were also displays but that distances must be in miles or yards. I’ve yet to find anything though which mentions weight limits… current laws specify the use of metric but I’m having a hard time persuading local authorities near where I live to fix signs which still read “tons” (which is quite frustrating when the BWMA seem to do so well getting perfectly good metric signs removed!)


  2. I don’t know the detailed history, but I’ve recently heard metric signs objected to because they contravene The Traffic Signs Regulations and General Directions 1994.


  3. David, The Traffic Signs and General Directions 1994 were superceded in 2002 by the Traffic Sign Regulations and General Directions 2002.


  4. All I can say is if I ever flaten some poor road worker I’ll be using the metric mess as my defence. If I see a sigh telling me of something to expect in yards I have no clue at all how long before I should expect it. And since stopping distances are tested in meters it makes even less sense. If there is something I need to be aware of on the road I should not be left tring to convert between two mesurement systems to know when to brake. What was that clunk?


  5. I’ve been talking to somebody who seems to know some of the answers to the questions asked.

    It seems that the use of “tonnes” for weight limits was introduced in 1981. Given savings regulations (which allows older signs to stay up until they wear out to save money) all of the old “tons” signs should now be gone, but clearly they haven’t.

    It’s believed that metric weight and hight limit signs were introduced at about the same time but didn’t get much use until after 1991.


  6. where i live, in york there are a scattering of signs that display in metric ie. blue signs that state, “narrow lanes for 1000m” yet further down the road another sign displays yards. what a mess we’re in!!!


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