Each lot shall abut on a street dedicated by the subdivision or an existing publicly dedicated street, or on a street which has become public by right of use and is more than fifty (50) feet wide except when approved by the Planning Commission as a Planned Unit Development. Interior lots having frontage on two (2) streets shall be prohibited except where topographic conditions make such design desirable. (PZSC § 03-28-005 (4) (C))