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Refined-scale crash data analysis using multi-level regression models


Road traffic safety has long been a major public health problem for the general public and government agencies. Nevertheless, road traffic crashes continue to bring immeasurable pain and suffering to the society, as well as high financial expenses associated with medical bills and lost productivity. After identifying some key research gaps related to the existing crash modeling such as lack of insightful modeling of crash rates, time-varying explanatory variables, serial correlation, unobserved heterogeneity and multiple dependent variables, the objective of this dissertation is to narrow these gaps by systematically developing advanced multilevel models for traffic safety modeling. It is expected that series of new crash models developed in this dissertation not only contribute to the state-of-the-art crash modeling, but also add to the knowledge toward developing proactive traffic management strategy. The dissertation has eight chapters: Chapter one provides some background information and literature review. Chapter two presents crash rate analysis with data in refined scales to quantify the relation between crash rate and time-varying variables along with other contributing factors. In Chapter three, the unobserved heterogeneity issue on mountainous highways crash rates is examined by developing an advanced random parameter tobit model with panel data in refined temporal scale. Chapter four proposes a correlated random parameter marginalized two-part model as an alternative to study the relationship between crash rate and its contributing factors. Chapter five examines the differences of contributing factors towards injury severity on mountainous (MN) and non-mountainous (NM) highway crashes using mixed logit models. Chapter six studies the effects of weather and traffic characteristics on single-vehicle and multi-vehicle crashes jointly by proposing a multivariate count data model which addresses unobserved heterogeneity across multiple dependent variables. In Chapter seven, a framework of Bayesian multivariate space-time model that can address spatial correlation/heterogeneity, temporal correlation/heterogeneity, and the correlation between different injury severities is introduced. Chapter eight concludes this dissertation by summarizing major findings and sharing some observations in terms of future research.


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traffic safety
crash data analysis


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