16.—(1) Subject to sub-paragraphs (2) to (4), the sign may remain in place for a period of six months beginning with the day the sign is placed.
(2) The period may be extended with the approval of—
(a)the Secretary of State in relation to a road in England;
(b)Scottish Ministers in relation to a road in Scotland; or
(c)Welsh Ministers in relation to a road in Wales.
(3) In the case of a sign conveying a change in route number, the period is two years, not six months.
(4) Sub-paragraph (1) does not apply to a sign—
(a)placed only in connection with the execution of works on or near a road, or a temporary obstruction;
(b)conveying information about check points at which goods vehicles or public service vehicles may be required to stop; or
(c)indicating diversions.