6.—(1) The triangle must be legibly and permanently marked with the specification number of the British Standard for an Advance Warning Triangle to indicate a temporary obstruction, namely BS AU47: 1965(1) or the specification number of a corresponding EEA standard.
(2) The surface coloured red and marked A must be reflectorised.
(3) Not more than 15 square centimetre of the surface marked A may be obscured by constructional components.
(4) The surface coloured red and marked B must be fluorescent.
(5) The surface marked C must be either—
(a)entirely reflectorised; or
(b)a combination of reflectorised and fluorescent.
(6) Not more than 10 square centimetre of the surface marked A may be obscured by constructional components.
(7) Corners of a triangle must be radiused.
(8) All sides of a triangle must be of the same length.
(9) The reflectorised areas of the surface may be internally illuminated provided that such illumination is steady, presents a uniform appearance throughout that area and does not impair the retroreflecting properties of that area of the surface.
(10) The triangle must not be illuminated through external illumination.
Publication date 15th January 1965 (ISBN 0580045013); amended by amendment number 1 of 6th May 1966.