(1) Each of the following periods or series of periods of driving shall be an excessive period for the purposes of this section:

(a) any continuous period of driving exceeding five and one-half hours;

(b) any series of continuous periods of driving amounting in the aggregate to more than eleven hours in any period of twenty-four hours beginning two hours after midnight;

(c) any period or series of periods of driving so arranged that the driver has not at least ten consecutive hours for rest in every period of twenty-four hours beginning at the commencement of any period of driving.

(2) For the purposes of subsection (1) of this section -

(a) Where a driver has at least nine consecutive hours for rest in a period of twenty-four hours beginning at the commencement of a period of driving, the period of at least nine consecutive hours shall be reckoned as a period of ten consecutive hours if the driver has at least twelve consecutive hours for rest in the twenty-four hours next after the expiration of the above-mentioned period of twenty-four hours;

(b) any two consecutive periods of driving shall be regarded as one continuous period unless they are separated by an interval of not less than half-an-hour during which the driver can obtain rest and refreshment;