Agenda - Planning Commission - 03/07/1995

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T~S JANUARY 1995 AMERICAN PLANNING ASSOCIATION Statistical A nalysis of Residential Lots By Cyrus K. Motlagh Sometimes, in correctingla problem, munii:ipal governments create new headaches along with opportunities. Take the village of Franklin, Mich{gan, which introduced pressure sewers, inducing some re&idents to split their oversized lots and sell the new pieces. ~his option had not been available without the sewers. But lots in this community are very valuable, and sometimes a resident finds that his howe is so situated that a clean and simple split is not possibleJ Snlitting these lots had not been the ong,nal ~ntenuon. As a result, some residents try to meet the black letter of the zoning dsdinance, relative to minimum lot size, by carving minimally iufficient square footage around existing structures withoutlregard[, tO the shape of the new lots 'being created. Neither the [~oning ordinance nor the lot split' ordinance have shape requirements, so officials are often faced with laws thai permit a split, even when common sense tells them such a split is unwise4 - -' Municipalities realize ~ey rieed regulations that would prevent the creation of biz~rely shaped lots but find it difficult to define the vexing notion[ of the complexity of the shape of a lof. This issue of Zoning ~V~os presents an attempt at a workable definition that could form ~e basis for legislation. It features a brief verbal description of {he statistical approach and factors in its favor, followed by a description of the Franklin~ Village and its situation. Itf also presents two propo'salsI for splits. Simplicity of the Statistical Approa4~h The statistical approach presented here is deceptively simple. The complexity (number of sides) of the log resulting from a proposed s~ht is compared with the distribution of number of sides among the lots in the rest of the community. If ~e complexity of one or both falls in the outer fringes or,his distribution, the proposed~ split is rejected or subjecte4 heightened scrutiny, where the applicant must produc8 reasons beyond commerci4 advantage for the strange shape of the proposed lots. Franklin Village and the sites of two proposed lot splits. Three questions immediately arise: · What is the deflr~ition of"the fringe" of the distribution? · Is regulation of lot complexity a reasonable exercise of governmental power? · Why use the number of sides complexity? Mean (acres) ~. ~ 0.41 ~1~. 0.68 StandardDev~'~0'27 ~ 0'26 ~ 0'83 Coefficient ~ [~Jl 0.38 ~ 0.42 of Variation 0.66 Minimum 0Al p.roe count 8nb 8rd. ~/A % Sub Std. ~ ~ N/A Theoretical LotssubJec, ~ to split as % of total lots N/A 4.1 0.0 TABLE 1: Size dislribution of lots, measured in acres, within varioub zoning classifications. Total includes two lots zoned restricted office and three R4 (very rare) lots. of a lot as the measure of its Where is the Outer Fringe? For statistical purposes, percentages in single digits generally have been accepted as rare, meaning that any characteristic not shared by at least 10 percent of the population may fairly be labeled as .rare or not in harmony with the character of the population. The choice of a particular percentage rests ultimately with community planners and the degree of uniformity that the community desires. The higher the percentage chosen, the more uniform the community will become in the long run. In larger communities, where a complete census of the lots is impossible, a random sample can be used for these purposes, but the sample must be very large. '79