The purpose of this document is to provide requirements, recommendations and guidance for onboard train protection systems and establishes industry standards for these systems. Onboard train protection systems are implemented to reduce the risk of accidents or incidents due to driver error or incapacity. The scope of this Standard is constrained to onboard train protection systems (OTPSs) as fitted to new, modified or existing self-propelled locomotive, passenger and infrastructure rolling stock.The document covers the application, design, interface, construction and maintenance of onboard train protection systems.The onboard train protection systems specifically covered in this document are:(a) vigilance system;(b) mechanical train stop and trip gear system (MTSTGS);(c) Automatic Warning System (AWS);(d) Train Protection and Warning System (TPWS);(e) Station Protection System (SPS);(f) operator enable system (OES);(g) automatic train protection system (ATP).