2.—(1) Subject as hereinafter provided, the amount of a motor vehicle allowance payable at the essential user’s rate shall, in any year, comprise a fixed element and a mileage element, calculated as provided in sub-paragraphs (2) and (3).
(2) The fixed element shall be calculated by reference to the number of completed months comprised in the period of authorised use for the year in question, at such annual rate as is specified by the Secretary of State by reference to the cylinder capacity of the motor car in question.
(3) The mileage element shall be calculated, in relation to authorised use, at such rate as is specified by the Secretary of State by reference to the cylinder capacity of the motor car in question, and for that purpose he may so specify –
(a)a basic rate, in relation to authorised use not exceeding such mileage as is specified by him (“the basic mileage”), and
(b)a reduced rate, in relation to authorised use in excess of the basic mileage.
(4) Where, in any year, a motor vehicle allowance is payable at the essential user’s rate, it shall be payable in such instalments, in advance or in arrear, as the Chief Constable may determine; but when the amount of the allowance for that year is finally calculated, any overpayment shall be recoverable.
(5) Where, in any year, a motor vehicle allowance is payable at the essential user’s rate to a member and –
(a)the member is on sick leave or maternity leave, or
(b)the motor car in question is out of order,
for a continuous period of four or more weeks in that year, the allowance shall be reduced by such amount as the Chief Constable determines as being appropriate in all the circumstances.
(6) Where, in any year, a motor vehicle allowance is payable at the essential user’s rate but the period of authorised use is a fraction only of that year, sub-paragraph (3) shall have effect as if for the reference to the basic mileage there were substituted a reference to the corresponding fraction of that mileage; and, for the purposes of this paragraph, the monthly rate of the fixed element of such an allowance so payable shall be taken to be a twelfth of the annual rate.