Reid Ewing & Susan Handy
Ewing, R. & Handy, S. (1). Measuring the Unmeasurable: Urban Design Qualities Related to Walkability. Journal of Urban Design, 14(1), 65–84. http://dx.doi.org/10.1080/13574800802451155
This study attempts to comprehensively and objectively measure subjective qualities of the urban street environment. Using ratings from an expert panel, it was possible to measure five urban design qualities in terms of physical characteristics of streets and their edges: imageability, enclosure, human scale, transparency and complexity. The operational definitions do not always comport with the qualitative definitions, and provide new insights into the nature of these urban design qualities. The immediate purpose of this study is to arm researchers with operational definitions they can use to measure the street environment and test for significant associations with walking behaviour. A validation study is currently underway in New York City. Depending on the outcome of this and other follow-up research, the ultimate purpose would be to inform urban design practice.
This study defines objective measures of urban design qualities: imageability, enclosure, human scale, transparency and complexity. Imageability makes a place distinct, recognizable and memorable and places with high imageability create a lasting impression. Enclosure is the degree to which streets and other public spaces are visually defined by buildings, walls, trees and other vertical elements and room-like spaces have proportionally related width and height of vertical elements . Human scale refers to a size, texture, and articulation of physical elements that match the size and proportions of humans and correspond to the speed at which humans walk such as building details, pavement texture, street trees, and street furniture. Transparency refers to the degree to which people can see or perceive human activity beyond the edge of a street including walls, windows, doors, fences, landscaping and openings into mid-block spaces. Complexity refers to the visual richness of a place and depends on the variety of the physical environment, specifically the numbers and types of buildings, architectural diversity and ornamentation, landscape elements, street furniture, signage and human activity.
Description of method used in the article
A panel of 10 urban design and planning experts was assembled from professional practice as well as academia. The panel members helped to qualitatively define urban design qualities of streetscapes, rated different scenes with respect to these qualities, submitted to interviews as they assigned their ratings to provide the research team with qualitative insights into physical features that influenced their ratings, met to discuss ways of measuring urban design qualities, and reviewed and commented on the draft field survey manual that presented the measurement instrument in all its detail. Expert panel ratings were used as dependent variables in the estimation of statistical models. The physical characteristics of the street environment were the independent variables.
Of practical use