Urban rail systems are increasingly reaching their limits as traffic demand rises. The safety and performance of these transport systems are significantly determined by the control and safety technology used. Expanding the transport offering requires efficient signaling systems, known as Communications-Based Train Control (CBTC) systems. In this book, the author presents the system environment into which CBTC systems are integrated within urban transport companies. It shows how the individual safety functions of CBTC solutions contribute to hazard control and how technical systems progressively take over more functions from humans with increasing grades of automation. Finally, non-functional requirements for CBTC systems such as safety, availability, performance, and cost-effectiveness are discussed, and factors for the successful execution of complex signaling renewal projects are highlighted.