Such differences would impress any urban planner and would be of primary importance for a developer. From the 57% of the former to the 75% of the latter there is an approximate 30% jump in land use efficiency. What is perhaps more instructive however, is the amount of difference between a low performing grid (e.g. The trend lines in the chart reveal the inverse relationship of ROW width to the efficiency of land use, as might be expected. This finding confirms the earlier assessment. To analyze the data, we did two types of calculations: a) we measured the land use efficiency of each one in the set by calculating the ratio of buildable (or saleable) land to the total land that includes the right-of-ways (ROW) for streets, as platted and b) we did the same calculation by adopting a constant ROW for all in order to see the effect of the grid frequency (street frequency or street density).įigure 1: Chart showing the influence of the right-of-way width on developable land.Ĭhart one finds Portland as the third least efficient of 20 urban grids with a buildable land use ratio of 59% and an implied 41% of land dedicated to ROWs. It consequently raises the inevitable question as to which would be a suitable candidate for a contemporary "town", "Planned Unit" or a suburban subdivision, if any at all. The present analysis focuses exclusively on comparing land use efficiency among the twenty grids. These gridiron layouts also span a range of street right-of-ways (ROW) from 30 feet to 120 feet. Portland grid, with Pioneer Square in the center (image from Google Earth)įor this analysis, we used twenty city grids that range from a mere 150 by 150 feet, just over one half acre, to the ten acres of the largest American grid of Salt Lake City (660 by 660 feet). We argued earlier that if the merits of the specific Portland grid plan were self-evident to planners or developers, its use would have been expanded in the city beyond the original plating of 1846 and imitated by other cities, neither of which has been the case. New data provided by Daniel Nairn on other American city grids has emerged since, and is analysed here, shedding more light on this assessment and also providing an opportunity for refined versions. We looked at Portland's 200' by 200' block in the context of other layout options and, when we compared it on a number of criteria, it did not fare well. In an earlier article we discussed the flaws with Portland's grid, most prominent of which was its inefficiency of land use. What is the preferred layout for a new neighbourhood? It's a question we have discussed previously in the pages of Planetizen, and one we'd like to return to again, with some interesting new research to consider.
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