Ballast plays a vital role in transmitting and distributing train wheel loads to the underlying sub-ballast and subgrade. Bearing capacity of track, train speed, riding quality and passenger comfort all depend on the stability of ballast through mechanical interlocking of particles. Ballast attrition and breakage occur progressively under heavy cyclic loading, causing track deterioration and rail misalignment-affecting safety and demanding frequent and costly track maintenance. In the absence of realistic constitutive models, the track substructure is traditionally designed using empirical approaches. In Advanced Rail Geotechnology: Ballasted Track , the authors present detailed information on the strength, deformation and degradation, and aspects of fresh and recycled ballast under monotonic, cyclic, and impact loading using innovative geotechnical testing devices. The book presents a new stress-strain constitutive model for ballast incorporating particle breakage and validates mathematical formulations and numerical models using experimental evidence and field trials. The text also elucidates the effectiveness of various commercially available geosynthetics for enhancing track drainage and stability. It presents revised ballast gradations for modern high-speed trains capturing particle breakage and describes the use of geosynthetics in track design. It also provides insight into track design, capturing particle degradation, fouling, and drainage. This book is ideal for final year civil engineering students and postgraduates and is a solid reference for practicing railway engineers and researchers with the task of modernizing existing track designs for heavier and faster trains.