The FAA safety Risk Management Guidance: The 5-Step Process (dated September 14, 2012) states "one of the fundamental principles of system safety is the safety order of Precedence eliminating, controlling, or mitigating a hazard. Safety professionals use the techniques listed in the Safety order of Precedence, in priority order, for reducing risk." The priority order is
1. Design the hazard out
2. Provide physical guards or barriers
3. Provide warning devices
4. Train people
5, Communicate the hazard