151.Section 171 sets out the basic elements which must be included in the order establishing the charging scheme - the roads to be charged, and how the charges are defined, the classes of motor vehicles which will be charged, the levels of charge, and the duration of the scheme. These elements are for the charging authority to determine. Section 171(3) ensures that charging powers cannot be used purely as a charge on parked vehicles.
152.Section 171(5) describes some of the factors by which different charges might be imposed, but this is not an exhaustive list. Section 171(7) allows the charging scheme to require documents or equipment to be carried in or fitted to a vehicle when it is on a charged road. This gives charging authorities the power to ensure that everyone who enters a scheme must have a permit or electronic payment unit in their vehicle, or have to pay a penalty charge.
Section 172 provides the power for regulations to set exemptions from charges, reduced rates or limits on charges which will apply to all charging schemes.   The Secretary of State will be able to set exemptions, reduced rates or charging limits applying to all local authority schemes in England (and has powers to set exemptions in London under the Greater London Authority Act 1999 (“the 1999 Act”)). This could be used for an exemption, for example, for emergency vehicles or disabled persons. The NAW also has powers to set exemptions, reduced rates or limits applying to Welsh local charging schemes.  Subject to these regulations, section 172(2) provides that any charging scheme will be able to set additional exemptions, reductions or limits as the authority wishes, subject to approval.
Commentary on Sections Part Iii: Road User Charging and Workplace Parking Levy Chapter I: Road User Charging Sections 171 to 172: Contents of charging schemes