# The Traffic Signs Regulations and General Directions 2016, Paragraph 25

Extent: E+W+S

(1) Identification numbers of routes—
(a) may be varied and may include capital letters; and
(b) where indicating a route to which a particular route leads, may be shown in brackets.
(2) When a route (other than a national or regional cycle route) is indicated, the route number and background of the route number patch may be in any contrasting colours but, if the route number patch has a light background, the white edge must be omitted.

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Source: https://www.legislation.gov.uk/uksi/2016/362/schedule/11/paragraph/25 (the official version)
Page: https://openlegislation.uk/traffic-signs-regulations-and-general-directions-2016/schedule-11/paragraph-25
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.