(4) Every letter and numeral incorporated in a temporary sign other than any letter incorporated in the sign in accordance with the provisions of paragraph (6) shall be not less than 40 nor more than 250 millimetres in height and every arrow so incorporated shall be not less than 250 nor more than 200 millimetres in length except that where an arrow is incorporated in the index part of a sign with a pointed end such arrow shall be not less than 100 nor more than 200 millimetres in length.
(5) Every letter, numeral, arrow, chevron or symbol incorporated in a temporary sign shall be—
(a) black on a background of white; or yellow; or
(b) white on a blue background
(6) There may be incorporated in, or attached to, a temporary sign the arms, badge or other device or a highway authority, police authority or an organisation representative of road users, or words or letter indicating the highway authority, or that the sign is a police sign.
(7) No sign shall by virtue of this Regulation convey to traffic any infromation, warning. requirement, restriction or prohibition or a description which can be so conveyed either by a sign shown in a diagram in Part I, Part II or Part IV of Schedule 1 or by a sign so shown used in combination with or in conjunction with another sign shown in such a diagram.
28.—(1) Beacons showing on intermittent amber lights for conveying the warning that drivers of vehicles should take special care may be used in combination with any of the signs specified in the last preceding Regulations or with any or the signs shown in diagrams 562 to 569.1, 569.3 or 610 subject to the following conditions:—
(i) the light emitted by the lens or lenses or each such bacon shall be of peak intensity of not less than 100 candelas on the principal axis or the relevant lens;
(ii) the part or that beacon through which light is emitted shall be of such a shape and size that the perimeter of the area projected horizontally thereby on to any vertical plans shall he capable of lying wholly inside a square having sides of 200 millimetres in length and wholly outside a square having sides of 100 millimetres in length;
(iii) the height of the centre of the lenses from the surface of the carriageway in the immediate vicinity shall be not less than 800 nor more than 1500 millimetre: and
(iv) the rate of flashing shall be not less than 120 nor more than 150 flashes per minute and the period between flashes shall not exceed ¼ of a second.
(2) Beacons showing an intermittent blue light for conveying the warning that drivers or vehicles should take special care may be used by a constable, or a person acting under the instruction (whether general or specific) of the chief officer of police, in combination with any or the signs shown in diagrams 606, 609, 610 and 633 to 635 subject to the same conditions specified in paragraph (1) (iii) and (iv).
(3) Flags of an area of not less than 0.2 square metres and coloured red for conveying the warning that it would be dangerous for drivers to cause their vehicles to proceed may be used in an emergency at or in the vicinity of works being executed, or or an obstruction situated on or near a road.
