Entrance and exit drives crossing a street line shall be limited to two along the frontage of any one street and the centerlines shall be spaced at least 75 feet apart and at least 150 feet from the street line of any intersecting street. Continuous open driveways in excess of 16 feet resulting in the elimination of curbing along streets shall be prohibited except that for commercial manufacturing and industrial uses driveways may be permitted with the approval of the Planning Board but in no case shall a driveway more than 16 feet in width be permitted without provision for a five foot island. Curbing at the driveway shall be depressed.