Based on the analysis of failure mechanism and the fault transmission process of the URT system, this paper establishes the state transition and dynamic redundancy degradation model for the URT's 2×2 redundancy vehicle control system, and then proposes an integrative available assessment indicator for vehicle control system. The GSPN is used in this paper to establish the behavioral model of signal transmission and voting activity in the vehicle control system and analyze its available influencing factors. The impacts of fault monitoring device performance and redundancy management strategies on the availability and operational safety of the vehicle system are also considered in this paper. Furthermore, this paper analyzes the influence both of the signal transmission correct rate and the false alarm rate of the fault monitoring device on the availability of the vehicle control system and the impact of the missed detection rate of the fault monitoring device on the dangerous state probability of the vehicle control system are analyzed. The variation of the system signal transmission delay caused by the failures is obtained. Finally integrating the above multiple performance measurements together, a comprehensive availability evaluation indicator is proposed in this paper, by which, the purpose of ensuring the safe and available operation of the urban rail train will be achieved.