Glossary · Risk assessment and risk reduction
Three-step method
In machine safety, the three-step method is the ISO 12100 order of risk reduction: first inherently safe design measures, then safeguarding and complementary protective measures, then information for use. Each step is applied only to the extent the previous one cannot reduce risk adequately.
- Machine safety
- Risk assessment
- EU
In one sentence
The three-step method orders machine risk reduction: design out the hazard, then safeguard it, then inform users about the risk that remains.
Example
For a CNC milling machine, the designer encloses the work zone completely (step 1), adds an interlocked door with guard locking (step 2) and describes residual risks during tool changes in the manual (step 3).
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Machine safety: Step 1 changes the design; step 2 adds safeguarding and complementary protective measures such as the emergency stop; step 3 provides information for use: warnings, signs and instructions.
- EU: The essential health and safety requirements of EU machinery legislation set the same order of principles. It is the basis of the harmonized standard ISO 12100.
- Technical documentation: Information for use is a real step of risk reduction, not a formality, but it must not be used to compensate for missing design or safeguarding measures. The risk assessment should show why each step was not enough on its own.
- Evidence: For each hazard, record which step addressed it and why higher steps were not practicable.
Safeguard vs. information for use
A safeguard acts on the hazard or on access to it. Information for use acts only through people reading and following it. The three-step method keeps these apart, so that a warning is never accepted in place of a practicable safeguard.