According to the grade of automation, the fully automatic operation (FAO) system of an urban rail transit can be divided into driverless train operation (GoA3) and unattended train operation (GoA4). FAO is a typical functional requirement about “center intensive control, and fast recovery of faults.” The signal system is the core of FAO. In view of the above- mentioned facts, this paper expounds on the importance of the system architecture and function of the optimized design scheme when the signal system transitions from level GoA2 to level GoA4. Beginning from the event of a center controlling train directly, this paper focuses on a center centralized control, equipment safety and reliability, and a fast recovery of faults. Optimization suggestions that provide a reference direction for improving the reliability and stability of FAO systems are raised with intelligent detection equipment that adopts a dual active center, fully electronic interlock, integrated radar, and video analysis technology.