The central question posed in this dissertation is concerned with the role that the built environment has in people's travel behavior. The built environment is examined in terms of psychological and objective aspects of the quality of the walking environment that might affect travel patterns. To examine the relationship between these two aspects of the built environment and travel behavior, this dissertation analyzes people's transit-use patterns and choice of travel modes using the Los Angeles County sample which is a subset of the data from the 2009 National Household Travel Survey California Add-on. ? This study first examines whether the perceptions that low-income people have about the walking environment affect their willingness to use public transportation by analyzing self-reported frequency of transit use and measured neighborhood attributes. A principal component analysis is used to reduce many overlapping perceptional variables to latent factors that are used in subsequent models of transit use. Four perceptional attributes are identified that affect regular transit use, i.e., physical safety, personal safety, amenities, and perceived isolation. The results of this study show that unfavorable perceptions of environmental conditions are independently associated with decreased transit use