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 in 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 barriers
3.Provide warning devices
4.Train people
5.Communicate the hazard
14.3Making Decisions About risk mitigations