4The following provisions shall have effect as regards the provisions of this Act mentioned in sub-paragraph (c) of paragraph 1 of this Schedule, namely,—
(a)if the provisions of the Road Traffic Act, 1956, specified in that paragraph (hereinafter referred to as the " old provisions ") are, as respects all vehicles to which they apply, in operation immediately before the commencement of this Act, the said provisions of this Act (hereinafter referred to as the " new provisions ") shall come into operation at that commencement;
(b)if the old provisions come into operation, as respects all such vehicles as aforesaid, at that commencement, the new provisions shall come into operation immediately thereafter;
(c)if the old provisions come into operation after that commencement on the same day as respects all such vehicles as aforesaid, the new provisions shall come into operation immediately after the old provisions come into operation ;
(d)if different days are appointed for the coming into operation of the old provisions as respects vehicles registered at different times, and those days do not fall before that commencement, then—
(i)in relation to a vehicle as respects which the old provisions are in operation immediately before that commencement, the new provisions shall come into operation at that commencement;
(ii)in relation to a vehicle as respects which the old provisions come into operation at that commencement, the new provisions shall come into operation immediately thereafter;
(iii)in relation to a vehicle falling within neither head (i) nor head (ii) of this sub-paragraph, the new provisions shall come into operation immediately after the old provisions come into operation as respects it.