(Georgia Institute of Technology, 2005-08-08)
Dumbaugh, Eric
Transportation safety is a highly contentious issue in the design of cities and communities. To enhance community livability, urban designers, architects and city planners often encourage the placement of street trees, aesthetic street lights, and other roadside features in a buffer zone between the pedestrian realm and the vehicle travelway. While such designs clearly enhance the aesthetic quality of a roadway, conventional geometric design practice regards roadside features located in the clear zone as fixed-object hazards, and strongly discourages their use. This study examines roadside safety in urban environments to better understand the nature of urban fixed-object crashes, as well as the safety impacts of livable streetscape treatments.
While the prevailing assumption is that livable street treatments have a negative impact on a roadways safety performance, the existing empirical evidence indicates that such designs are much safer than more conventional roadside designs. Current safety objections to the use of livable street treatments are not based on empirical evidence, but are instead the result of a design philosophy that systematically overlooks the real-world operating behavior of road users.
This study details the origin and evolution of this philosophy, termed passive safety, and subjects it to an empirical test to evaluate its applicability to urban arterial roadways. It finds that passive safety assumptions do not meaningfully explain empirical observations of crash frequency and severity. To enhance contemporary geometric design practice, this study then proceeds to more thoroughly examine the nature and characteristics of urban roadside crashes, and proposes a new design approach, termed positive design that better addresses the twin goals of safety and livability.
(Georgia Institute of Technology, 2005-04-20)
Lee, Sugie
This dissertation investigates the impact of metropolitan growth patterns and policies on both intra-regional spatial differentiation and the decline of inner-ring suburbs by identifying a multi-ring metropolitan structure in four metropolitan areas of Atlanta, Cleveland, Philadelphia, and Portland, using longitudinal Census data from 1970 to 2000.
The findings of this research confirmed that intra-regional spatial differentiation increased over time and showed that the inner-ring suburbs in the four metropolitan areas were increasingly vulnerable to socioeconomic decline regardless of their growth patterns and policies. In contrast, the downtowns and some parts of the inner city showed gradual recovery from the deterioration patterns of the last several decades. The outer-ring suburbs continued to thrive, drawing most of the new population and housing development.
This dissertation also explored the association between metropolitan growth patterns and policies and the extent of spatial differentiation and socioeconomic disparity in the subareas. Analyses found that strong decentralization trends are associated with increases in intra-regional spatial differentiation and socioeconomic disparity, while urban containment policies are associated with their reduction. However, despite its strong urban containment policies, the Portland region exhibited a clear pattern of inner-ring suburban decline, which suggests that the inner-ring suburbs require local initiatives directed toward revitalization.
In conclusion, this research has shown that excessive development at the urban fringe is associated with the abandonment of the blighted inner city and more importantly, in the decline of the inner-ring suburbs. The inner-ring suburbs, with their existing valuable assets, should be fertile grounds for smart growth strategies. Moreover, the central city and outer-ring suburbs have a vital mission to save and invigorate the inner-ring suburbs, as they represent the primary link and conduit to all the surrounding areas of a metropolitan region. Only by recognizing the interdependence of all the areas and by applying sound, holistic policies can the decision-making entities of the government ensure the survival and future stability of the metropolitan areas.