Lots having double frontage shall not be approved except where necessitated by topographic or other unusual conditions. The width of each block shall be sufficient for an ultimate layout of two tiers of lots therein of a size required by the provisions of this title unless the general layout in the vicinity; lines of ownership; topographical conditions, or locations of arterial streets or freeways justify or make necessary a variation from this requirement. (Ord. 1046 NCS §1 (part), 1972; prior code §22.7.410.)