# Traffic Signs (Temporary Obstructions) Regulations (Northern Ireland) 1999, Paragraph 4


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. The triangle shall not be directly illuminated externally.

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Source: https://www.legislation.gov.uk/nisr/1999/121/schedule/3/part/2/paragraph/4 (the official version)
Page: https://openlegislation.uk/traffic-signs-temporary-obstructions-regulations-northern-ireland-1999/schedule-3/part-2/paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.