OK, not strictly on the issue of metric transport signs, I admit.

But we've recently been asked about all those unfriendly-looking black-on-yellow symbols that have been appearing on many road signs on motorways and major roads in the south-east - and I think throughout the country.

These symbols are metal plates about 9" square (or oblong) and consist of a black square, triangle, circle or lozenge (diamond shape on its side) on a bright yellow background. There are a further four similar-looking signs which consist of the same shapes - but in black outline only, not filled in.

They can be found on page 322 of the Traffic Signs Regulations and General Directions 1994.

Their purpose?

It says on page 322 that they are "symbols for use on directional signs to indicate diversion routes".

The relevant regulation states: "Symbols incorporated in signs for the purpose of indicating diversion routes to be followed in an emergency shall have the proportions and form shown in Part VII (7) of Schedule 13".

It's interesting that the colours black on yellow have been chosen for these symbols, because they are universally associated with danger. In the natural world, wasps, bees and hornets are all black-and-yellow, and international hazard signs e.g. on the backs of lorries are also black-and-yellow.

I looked up the regualation that I have quoted, i.e. the one that refers to Part VII (7) of Schedule 13.

The relevant regulation is Paragraph 13, sub-paragraph 7.

You can make of that little coincidence what you will.

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P.S. Are these signs appearing in other countries i.e. are they international?

Maybe someone's placing warnings that metric roadsigns will be here soon.......

Do I detect a hint of a conspiracy theory??

Honi soit qui mal y pense

Terrorism emergency??

I first became aware of these signs in 1978 - when I settled in the UK having decided that it was more stable than South Africa. Their role seems to have remained unchanged for the last quarter century.