17(1)A tower wagon used solely by, or by a person acting pursuant to a contract with, a street lighting authority for the purpose of installing or maintaining materials or apparatus for lighting streets, roads or public places is an exempt vehicle.
(2)In sub-paragraph (1)“tower wagon” means a goods vehicle—
(a)into which there is built, as part of the vehicle, an expanding or extendible device designed for facilitating the erection, inspection, repair or maintenance of overhead structures or equipment, and
(b)which is not constructed or adapted for use, or used, for the conveyance of any load other than—
(i)such a device or articles used in connection with it, or
(ii)articles used in connection with the installation or maintenance (by means of such a device) of materials or apparatus for lighting streets, roads or public places.
(3)In sub-paragraph (1)“street lighting authority” means a local authority, Minister or Northern Ireland department having power under an enactment to provide or maintain materials or apparatus for lighting streets, roads or public places.