5.—(1) This rule shall apply to a vehicle carrying a load which projects to the rear of the vehicle making the rear marking, fitted in accordance with rule 3(4)(b), so obscured by the load that the marking is not clearly visible within a reasonable distance to the rear of the vehicle.
(2) A vehicle to which this rule applies need not be fitted with a rear marking in accordance with rule 3(4)(b), if the marking which, but for paragraph (1), would be required by that rule to be fitted to the vehicle, is instead fitted to the load it is carrying.
(3) In relation to a rear marking fitted to such a load in the course of being carried, the provisions of Part III of the Schedule shall apply to that marking, subject to the following modifications:
(a)
in paragraphs 1, 4, 5 and 8 of that Part for any reference to the vehicle there shall be substituted a reference to the load; and
(b)
in rule 5(1) of that Part, for the words from “except while” to the end of that paragraph there shall be substituted the words “except while the load is being mounted on or removed from the vehicle”.