(1) For the purposes of this Act, the weight unladen of a vehicle or combination of vehicles shall be taken to be the weight of the vehicle or combination inclusive of all additions, but exclusive of the weight of water, fuel or accumulators (other than boilers) used for the purpose of propulsion and of loose tools or loose equipment.
(2) For the purposes of subsection (1) of this section -
(a) each of the following shall, with respect to a vehicle or combination of vehicles, be an addition:
(i) a body,
(ii) a part,
(iii) a fitting,
(iv) a receptacle,
(b) in a case in which there is one addition only, the reference to all additions shall be construed as a reference to that addition,
(c) in a case in which, there being two additions (and not more), on no occasion are both of them used, the reference to all additions shall be construed as a reference to the heavier only of the additions or, where they are of equal weight, to one of them only,
(d) in a case in which, there being three or
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