4(1)A fire engine is an exempt vehicle.
(2)In sub-paragraph (1)“fire engine” means a vehicle which—
(a)is constructed or adapted for use for the purpose of fire fighting or salvage (or both), and
(b)is used solely for the purposes of a fire brigade (whether or not one maintained under the [1947 c. 41.] Fire Services Act 1947 or the [S.I. 1984/1821 (N.I.11).] Fire Services (Northern Ireland) Order 1984).