Online

Harvey, Chester Wollaeger

Natural Resources

2014

MS

City streets are the most widely distributed and heavily trafficked urban public spaces. As cities strive to improve livability in the built environment, it is important for planners and designers to have a concise understanding of what contributes to quality streetscapes. The proportions and scale of buildings and trees, which define the three-dimensional extents of streetscapes, provide enduring, foundational skeletons. This thesis investigates how characteristics of such streetscape skeletons can be quantified and tested for appeal among human users. The first of two journal-style papers identifies a concise set of skeleton variables that urban design theorists have described as influential to streetscape appeal. It offers an automated GIS-based method for identifying and cataloging these skeleton variables, which are practical to measure using widely available spatial data. Such an approach allows measurement of tens of thousands of street segments precisely and efficiently, a dramatically larger sample than can be feasibly collected using the existing auditing techniques of planners and researchers. Further, this paper examines clustering patterns among skeleton variables for street segments throughout Boston, New York, and Baltimore, identifying four streetscape skeleton types that describe a ranking of enclosure from surrounding buildings--upright, compact, porous, and open. The types are identifiable in all three cities, demonstrating regional consistency in streetscape design. Moreover, the types are poorly associated with roadway functional classifications--arterial, collector, and local--indicating that streetscapes are a distinct component of street design and must receive separate planning and design attention. The second paper assesses relationships between skeleton variables and crowdsourced judgments of streetscape visual appeal throughout New York City. Regression modeling indicates that streetscapes with greater tree canopy coverage, lined by a greater number of buildings, and with more upright cross-sections, are more visually appealing. Building and tree canopy geometry accounts for more than 40% of variability in perceived safety, which is used as an indicator of appeal. While unmeasured design details undoubtedly influence overall streetscape appeal, basic skeletal geometry may contribute important baseline conditions for appealing streetscapes that are enduring and can meet a broad variety of needs.