(1)Duty at a higher rate does not become chargeable under section 15—
(a)where subsection (2) applies in relation to a tractive unit, by reason of the tractive unit being used in accordance with subsection (3),
(b)where subsection (4) applies in relation to a tractive unit, by reason of the tractive unit being used in accordance with subsection (5), or
(c)where subsection (6) applies in relation to a tractive unit, by reason of the tractive unit being used in accordance with subsection (7).
(2)This subsection applies in relation to a tractive unit where—
(a)a vehicle licence for—
(i)a tractive unit having two axles which is to be used only with semi-trailers with not fewer than two axles, or
(ii)a tractive unit having two axles which is to be used only with semi-trailers with not fewer than three axles,
has been taken out for the tractive unit, and
(b)the rate of duty paid on taking out the licence is equal to or exceeds the rate of duty applicable to a tractive unit having two axles which—
(i)has a plated train weight (or, in Northern Ireland, a relevant maximum train weight) equal to the maximum laden weight at which a tractive unit having two axles may lawfully be used in Great Britain with a semi-trailer with a single axle, and
(ii)is to be used with semi-trailers with any number of axles.
(3)The tractive unit is being used in accordance with this subsection where—
(a)it is used with a semi-trailer with a single axle, and
(b)when so used, the laden weight of the tractive unit and semi-trailer taken together does not exceed the maximum laden weight mentioned in subsection (2)(b)(i).
(4)This subsection applies in relation to a tractive unit where—
(a)a vehicle licence for a tractive unit having two axles which is to be used only with semi-trailers with not fewer than three axles has been taken out for the tractive unit, and
(b)the rate of duty paid on taking out the licence is equal to or exceeds the rate of duty applicable to a tractive unit having two axles which—
(i)has a plated train weight (or, in Northern Ireland, a relevant maximum train weight) of 33,000 kilograms, and
(ii)is to be used with semi-trailers with not fewer than two axles.
(5)The tractive unit is being used in accordance with this subsection where—
(a)it is used with a semi-trailer with two axles, and
(b)when so used, the laden weight of the tractive unit and semi-trailer taken together does not exceed 33,000 kilograms.
(6)This subsection applies in relation to a tractive unit where—
(a)a vehicle licence for a tractive unit having three or more axles which is to be used only with semi-trailers with not fewer than two axles has been taken out for the tractive unit, and
(b)the rate of duty paid on taking out the licence is equal to or exceeds the rate of duty applicable to a tractive unit having three or more axles which—
(i)has a plated train weight (or, in Northern Ireland, a relevant maximum train weight) equal to the maximum laden weight at which a tractive unit having three or more axles may lawfully be used in Great Britain with a semi-trailer with a single axle, and
(ii)is to be used with semi-trailers with any number of axles.
(7)The tractive unit is being used in accordance with this subsection where—
(a)it is used with a semi-trailer with a single axle, and
(b)when so used, the laden weight of the tractive unit and semi-trailer taken together does not exceed the maximum laden weight mentioned in subsection (6)(b)(i).