# The Traffic Signs Regulations and General Directions 2016, Paragraph 3

Extent: E+W+S

The peak intensity of light emitted by the lens or lenses of each beacon must be—
(a) if the period between individual flashes does not exceed ¼ of a second, not less than 100 candela on the principal axis of the relevant lens;
(b) if the period between individual flashes exceeds ¼ of a second, not less than 2000 candela on the principal axis; or
(c) if the period between the cessation of a double flash and the start of the succeeding double flash exceeds ¼ of a second, not less than 1000 candela on the principal axis.

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Source: https://www.legislation.gov.uk/uksi/2016/362/schedule/13/part/10/paragraph/3 (the official version)
Page: https://openlegislation.uk/traffic-signs-regulations-and-general-directions-2016/schedule-13/part-10/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.