# Traffic Signs (Temporary Obstructions) Regulations (Northern Ireland) 1999, Paragraph 1


The areas marked A, B and C in the diagram indicate areas of the surface on the face of the triangle as follows:
A — Red reflectorised surface. Not more than a total of 15 square centimetres may be obscured by constructional components.
B — Red fluorescent surface.
C — May have either red reflectorised surface or a combination of both red reflectorised and red fluorescent surface. Not more than 10 square centimetres in each corner may be obscured by constructional components.

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Source: https://www.legislation.gov.uk/nisr/1999/121/schedule/3/part/1/paragraph/1 (the official version)
Page: https://openlegislation.uk/traffic-signs-temporary-obstructions-regulations-northern-ireland-1999/schedule-3/part-1/paragraph-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.