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This research shows a methodology to address a long- standing question in traffic safety relating to the evaluation of safety risk and the benefits associated with safety interventions. Safety interventions are associated with selectivity bias problems. By proposing a joint model of heterogeneity and selection bias using a discrete- count approach via multiple scales, the methods in this research may provide guidance on incorporating bias from site selection into design contexts associated with high levels of unobserved heterogeneity. This in turn can provide focused guidance on the...

The original contribution of this thesis is two-fold: a) it addresses a gap in the published literature on the accommodation of potential information from segments that are observed to have not crashes, which as a result can affect the estimated severity distributions; and b) by accounting for such selection effects, the thesis also makes original contributions in the area of the nature of the impact of selection effects on parameters associated with severity models. In particular, the severity models are formulated as two-stage models where information on both geometrics and collision type...

Understanding the dynamics of nonmotorized human travel activity systems is of great importance for addressing national security concerns. Specific attention is focused on developing a systematic method for evaluating and identifying network vulnerabilities and conducting lifecycle risk assessments. Downtown Seattle in Washington State, due to its border proximity and multimodal accessibility, is the case study providing the empirical basis for this research. The analytical approach establishes a layered modeling framework that structures individual traveler activity information with...