Different classes of traffic may be prescribed by a scheme under section 7 of this Act in relation to different parts of the special road to which the scheme relates.

The classes of traffic prescribed by any such scheme shall be prescribed by reference to the classes set out in Schedule 3 to this Act.

The Secretary of State may by order vary the classes of traffic specified in the said Schedule 3 and the composition of any such class; and where any such order has come into operation, any reference in a scheme in force under the said section 7, whether that scheme was made or confirmed before or after the date on which the order comes into operation, to any class of traffic to which the order relates shall be construed as a reference to that class as varied by the order.