Off-site Parking in a Commercial District. Where there are practical difficulties in the way of the location of parking space or if the public safety or the public convenience or both would be better served by the location of such parking space other than on the same lot with the use to which it is appurtenant, the Board of Adjustment on specific application may authorize such alternative required parking space as will adequately serve the public interest, under the procedures for special permit uses, as described in this chapter.