In all cases where a lot in one ownership, other than a through lot, is divided by a district boundary so that 50% or more of such lot lies in the less restricted district, the regulations prescribed for such less restricted district shall apply to the more restricted portion of said lot for a distance of 30 feet from the zoning district boundary. For purposes of this law, the more restricted district shall be deemed that district which is subject to regulations which prohibit the particular use intended to be made of said lot or which regulations set higher standards with respect to setback, coverage, yards, screening, landscaping and similar requirements.