Transportation safety is a highly contentious issue in the design of cities and communities. While urban designers, architects and planners often encourage the use of aesthetic streetscape treatments to enhance the livability of urban streets, conventional transportation safety practice regards features such as street trees as fixed-object hazards, and strongly discourages their use. This dissertation examines the subject of urban roadside safety to better understand the safety impacts of livable streetscape treatments. It finds that there is little empirical evidence to support the assertion that livable streetscape treatments have a negative impact on a roadway’s safety performance, and substantial evidence indicating that they will actually enhance safety. Instead, the more substantive barrier to their use is a design philosophy that discounts the important relationship between driver behavior and safety performance. This dissertation traces the origin and evolution of this philosophy, and proposes an alternative approach, termed “positive design,” that better accounts for the existing empirical evidence on urban road safety, as well the dynamic relationships between road design, driver behavior and crash performance. (Author/publisher)
Abstract