More than ninety percent (90%) of the trips of each driver's working calendar day in any vehicle for which a certificate is issued pursuant to Section 20-156 must be to or from locations within Prince George's County. In order for a certificate to be renewed, the certificate holder must demonstrate that the vehicle for which the certificate has been issued and any replacement vehicle to which the certificate has been reassigned have been driven for a combined total of 26,000 miles in the previous twelve (12) months.