The rail industry used to manage fatigue by working to the Hidden Limits, which defined permissible work and rest periods for staff. We now know that the Hidden Limits did not offer enough protection from fatigue and recognise the need for a systemic approach. A Fatigue Risk Management System (FRMS) is an evidence-based, data-driven and documented process. It measures actual risks and enables a company to develop tailored controls to offset any potential increase in fatigue levels. In this section you will find guidance and resources aimed at people who want to learn about, set-up or run a FRMS.