A particular kind of street network is examined, where strong differentiation between scales of syntactic structure is evident: supergrids of primary roads, with inserted local streets. Computational formulae are provided to describe simple regular systems and clarify the nature of the syntactic differentiation of scales. The focus is on the linear extension of streets and also on distances measured according to direction changes. A small sample of examples from Chicago, Los Angeles, Beijing and Seoul as well as the Doxiadis plan for sector G7 of Islamabad and the Perry-Whitten neighborhood plan for New York are also analyzed, leading to estimates of a number of remarkably consistent parameters that can function as benchmarks for design exploration or theoretical experimentation. An experiment whereby the fabric of the historic centers of small French towns is inserted into a supergrid at 0.5 mile intervals is also described to explore the scale and character of inserted systems in comparison to historic urban fabrics. The work leads to a methodological proposition. Supergrids can best be conceptualized by decomposing the analysis of closeness centrality (integration) into two components: the mean directional distances associated with the supergrid as an independent system, and the mean directional distances from inserted streets to the nearest supergrid element (step depth in DepthMap). Decomposition responds to a theoretical idea: cognitive maps comprise a skeleton system relative to which other parts can be ‘placed’ and related. Decomposition responds to a practical purpose: in order to design one must work with intuitively accessible parameters that can be controlled within the site and scope of the design.
|The Journal of Space Syntax
|Early online date
|26 Oct 2015
|E-pub ahead of print - 26 Oct 2015