The maximum premium that the Board may determine to be payable at any time during the first year, second year or third year in respect of a motor vehicle of class 1 or 2 is, if its registered operator is one of the following persons, 80% of the premium that would, but for this clause, be payable in respect of that motor vehicle:

(a) a pensioner;

(b) a person who has a severe disability;

(c) a parent or guardian of a person who has a severe disability and has not attained the age of 16 years.