(1) For this regulation, the total mass of a vehicle or combination may be worked out using either of the following methods:
(a) the sum of the axle loads of the single axles and the axle group loads of the axle groups of the vehicle or combination;
(b) weighing simultaneously on a measuring instrument—
(i) all the wheels of the vehicle or combination; and
(ii) the vehicle or combination, together with its load (if any).
(2) For this section:
"axle group load", for an axle group of a vehicle or combination, is the sum of the axle loads of the axles of the axle group.