BAYESIAN SPATIO-TEMPORAL ANALYSIS OF ROAD TRAFFIC CRASHES Amin Azimian Road traffic crashes are one of the major causes of death and serious injury in the US, leading to economic losses and human suffering. In recent years, several research efforts have been made to screen areas and locate hotspots/zones and to identify the factors contributing to traffic crashes of different severity levels. Such research typically aggregates crash locations into spatial units at the macro level, such as counties, or at the micro level, such as road segments or intersections. Many crash estimation methods have been proposed in the literature. These methods range from classical approaches, such as the linear, Poisson, negative binomial, and logistic regression methods, to more state-of-the-art approaches, such as the empirical Bayesian (EB), spatial autoregressive, and full Bayesian methods. A considerable drawback of classical methods is that they cannot account for the regression-to-the-mean bias and potential unobserved heterogeneity, which can result in unstable and biased parameter estimates. Additionally, EB and spatial autoregressive methods are unable to address multilevel data and group-level random effects. By contrast, the full Bayesian framework is more flexible and can be easily extended to include random effect terms that can act as proxies for unobserved or missing covariates that have a spatial or temporal structure. Although the full Bayesian framework appears to be a promising methodology for dealing with crash data, the few previous studies in the area of road traffic safety that used this framework had some major limitations. Some studies performed their analyses in DEDICATION This dissertation is lovingly dedicated to my family. Your support and encouragement mean so much to me, and I am forever grateful. Thank you! v ACKNOWLEDGMENTS First, I would like to thank my advisor, Dr. V. Dimitra Pyrialakou. I am deeply honored to be her first Ph.D. student. I appreciate all her contributions in terms of her time, ideas, and efforts to make my Ph.D. experience truly productive and stimulating. The joy and enthusiasm she has for research were contagious and motivational for me, especially during the tough times in my Ph.D. pursuit. I also thank my committee members, namely, Drs. David Martinelli, Kakan Dey, Sijin Wen, Ashish Nimbarte, and Steven Lavrenz, for all their advice and support. Finally, I thank my family for their love, care, and support. Specifically, I express my immense gratitude to my lovely wife, Hanieh, for her patience and unparalleled support. My family is my biggest support system, materially and morally. vi