Creating traffic models is a complex task due to the intricacies of road networks, space-time dependencies, heterogeneous traffic patterns, and numerous interacting components. The second edition of Traffic Flow Theory builds on foundational knowledge to express these elements in mathematical form and offers updated coverage of the latest field developments. Authored by a leading academic, the volume dissects everyday traffic phenomena, detailing their characteristics, mechanisms, and dynamics through multi-level modeling approaches (macroscopic, microscopic, mesoscopic, and picoscopic) to explain why these phenomena occur and how they can be effectively simulated. The book then explores the practical applications of these simulations and contributes new, research-informed evidence showing that integrating the various analytical frameworks leads to a unified perspective--with significant benefits for optimizing safety and efficiency in transportation systems. With its comprehensive, coherent, and self-contained treatment, Traffic Flow Theory 2E is set to become a staple reference for a broad transportation engineering audience and a valuable resource for readers in interconnected disciplines.