This Publicly Available Specification covers general high-level safety requirements for all types of automated urban guided transit systems with independent self-propelled trains operating on an exclusive guideway.This PAS is not concerned with pre-existing DTO or UTO systems (for definitions, see 3.2) that were designed before this PAS took effect. In the case of upgrading an existing transit system to a DTO or UTO system, the risks associated with the existing system are outside the scope of this PAS. However, the risk assessment process described herein may be relevant, and its application is at the discretion of the safety authority having jurisdiction. In the case of extending or modifying an existing DTO or UTO system in operation, this PAS applies only if the change is significant as determined by the safety authority having jurisdiction; but the risks due to the relationship with the unchanged parts of existing systems (rolling stock, traction power supply, signalling, platforms) shall be taken into account. This PAS deals with safety requirements needed to compensate for the absence of the driver or attendant staff who are typically responsible for the activities mentioned in Table 1. Table 1 describes the relationship between the grade of automation and basic system functions.