# The Traffic Signs Regulations and General Directions 2016, Paragraph 12

Extent: E+W+S

(1) When the marking is used, studs may also be placed.
(2) The studs must incorporate—
(a) red reflectors;
(b) red retroreflecting material; or
(c) a light source that emits, during the hours of darkness, a steady red light,
or any combination.
(3) The studs must be fitted at the side of, and adjacent to the solid line forming the boundary of the marking.
(4) The external part of the stud that is visible when the stud is in place must be—
(a) red
(b) white;
(c) of a natural metallic finish;
(d) of another neutral colour; or
(e) clear,
or any combination (but see sub-paragraph (5) for an exception).
(5) The external part of a stud that is visible when the stud is in place temporarily during road works must be fluorescent green-yellow except to the extent—
(a) it consists of red reflectors or retroreflecting material; or
(b) it is necessary for it to be a different colour or clear in order for the stud to emit red light.

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Source: https://www.legislation.gov.uk/uksi/2016/362/schedule/9/part/8/paragraph/12 (the official version)
Page: https://openlegislation.uk/traffic-signs-regulations-and-general-directions-2016/schedule-9/part-8/paragraph-12
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.