A contributor asks whether the failure of UK signs to use the correct international symbols could enable lawyers to get their clients off fines for motoring offences.
One of the guiding principles of the SI Brochure [the manual of the BIPM – International Bureau of Weights and Measures, who regulate the metric system) is that each unit of measure should have its own unique symbol. All units of measure that are included have been allocated symbols. These symbols include:
- T (upper case) – teslas (strength of a magnetic field)
- t (lower case) – tonnes
- ‘ (single apostrophe) – minutes of arc
- ” (double apostrophe) – seconds of arc
(No symbol was allocated for “mile”, which should be written in full.)The SI manual formed the basis of the EU directive on metrication. When the British Government negotiated with the governments of our partners in the EU to retain the foot and inch, one of the clauses of the agreement extended the catalogue of units to include feet and inches for use in certain circumstances and subject to specified conditions. When they were incorporated into the catalogue, they were allocated the following symbols:
- ft – Feet
- in – inches
What has the UK Government done?
On height and width restriction signs, one sees feet and inches denoted by single and double apostrophes respectively, while on weight restriction signs, one sees “T” (upper case) used to denote tonnes on weight restriction signs (OK, the law permits a lower case “t”, but I have yet to actually see one on a road sign in Britain – the law in question is – Statutory Instrument 2002 No. 3113 – The Traffic Signs Regulations and General Directions 2002 – the “TSRGD”).
The TSRGD also allows the use of the symbol “m” sometimes to denote “mile” and sometimes “metre”.
To the best of my knowledge, this has yet to be tested in a United Kingdom court – if it were, would the court rule that these signs are unenforceable due to the technicality of the incorrect use of symbols? One must remember of course that under the European Communities Act 1972, the courts would be obliged to pass judgement “in accordance with the principles laid down by and any relevant decision of the European Court”.
If such a case heard in a UK court and the road signs declared unenforceable, the first people to be affected would be those people who live on a “rat-run” where heavy vehicles are prohibited by width and weight restriction signs. The councils representing such people can take preventative action against the these signs being declared unenforceable by ensuring that weight restriction signs use the lower case “t” to denote “tonnes” and that width restriction signs clearly display both metric and imperial units.
[Please note:
Neither the author nor UKMA are able to offer any formal legal advice. The views published above are the views of the author who has not had formal legal training. The UKMA do not necessarily endorse these views. If somebody wishes to pursue a matter based on these views through the courts, they should seek proper legal advice from their solicitor.]
[article submitted by MV]
Metric Views 
And yet for bridges and tunnels the height is nearly always given in metres, I notice these days. I’m sure it has been that way for many years now. I can’t remember the last time I saw a width restriction – I live in the very rural north of Scotland, and road signage almost doesn’t exist as it is! – so I can’t comment further on that.
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@Bob Phillips. I write this article 15 years ago. Since then the law has changed. All new weight restriction signs have “t” on them, rather than “T” and dual units are mandatory on new height and width restriction signs.
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In my school days, the maths teacher recommended m for metres and mi for miles. The latter has always been understood when I have used it subsequently. It is a pity that our successive governments have paid so little attention to international standards.
I recently saw a road sign warning of a low bridge ahead. the symbol m was used in two different ways on the same sign, representing metres for the bridge height and miles for the distance ahead.
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