21.—(1) The promoter may, if it considers it necessary or expedient in consequence of any works executed or proposed to be executed in a street along which an authorised street tramway is constructed—
(a)remove or discontinue the operation of the authorised street tramway; and
(b)lay, maintain and operate in that street or in a street near to that street a temporary street tramway in lieu of the authorised street tramway.
(2) The powers conferred by this article may only be exercised with the consent of the street authority but such consent must not be unreasonably withheld.
(3) The provisions of article 9(2) (power to alter layout etc., of streets), article 10 (power to keep apparatus in streets), article 11 (power to execute street works) and article 40 (traffic signs) apply in relation to any temporary street tramway laid under this article as they apply in relation to the authorised street tramway.