This standard covers general provisions for the evaluation of the technical competence of a vehicle test station authority. It also serves as a basis for determining the grading and registration of the authority on the grounds of its adherence to the provisions of this standard, the suitability of the equipment and the competence of the examiners employed. 2 The principal grades intended for such authorities are as follows: a) grade A - examination and testing of any class of vehicle; and b) grade B - examination and testing of motor vehicles other than a goods vehicle or a bus of gross vehicle mass exceeding 3 500 kg. 3 In addition, where the population of a rural area does not justify the introduction of a permanent vehicle test station, a mobile vehicle test unit that complies with the provisions of this standard and that is confined to a specific area should be allowed.