In basic terms, a safety management system (SMS) is a formal arrangement for managing, assuring, and improving safety. An SMS is not a single document, it is a framework for managing all risks that  arise from running a transport system. It defines roles and responsibilities, sets arrangements for safety mechanisms, involves workers in the process, and ensures continuous improvement.

The Railways and Other Guided Transport Systems (Safety) Regulations 2006 (ROGS) introduced the requirement for and content of an SMS. The regulations require most railway operators to maintain an SMS, and hold a safety certificate or authorisation indicating that the SMS has been accepted by the Office of Rail and Road.