Glossary · Risk estimation methods
Risk matrix
In safety engineering, a risk matrix is a matrix that combines severity and likelihood categories to support risk estimation or prioritization. Each cell assigns a risk level that guides whether and how urgently risk reduction is needed.
- Machine safety
- Risk assessment
In one sentence
A risk matrix places severity against likelihood to rank risks; it is a communication aid that needs defined categories to give consistent results.
Example
A plant uses a five-by-five risk matrix in which serious irreversible injury combined with occasional likelihood lands in the red zone, so the hazard at a press brake must be reduced before production resumes.
How it applies
- Risk estimation: A matrix is one way to combine severity and likelihood. Define each category in words, with examples, so that different people choose the same cell.
- Limits: Matrices compress information. Coarse categories can place very different risks in the same cell, and colors can suggest a precision that does not exist. Do not let the matrix replace reasoning.
- Functional safety: For safety functions, standards use their own schemes, for example the risk graph of ISO 13849-1 for the required Performance Level. A company risk matrix does not replace it.
- Technical documentation: Record the matrix version with the assessment. Changing the matrix later changes the meaning of all earlier ratings.
Risk matrix vs. risk graph
A risk matrix combines two dimensions in a grid. A risk graph, as in ISO 13849-1, walks through several parameters in sequence (severity, exposure, avoidance) to reach a required level.