What Is an Influence Diagram

An Influence Diagram is a visual modelling tool used to represent the relationships between decisions, uncertainties, and outcomes within a system. It helps simplify complex decision-making by showing how various factors influence one another—especially in risk assessment, stakeholder strategy, and operational planning.

In the context of ISO 45001-compliant Occupational Health & Safety (OH&S) systems, Influence Diagrams are valuable for understanding the systemic impact of stakeholder behaviours, identifying critical risks, and improving safety-related decision-making.

Key Components of an Influence Diagram

• Decisions: Represented as rectangles or ovals, these indicate available choices or actions.
• Uncertainties: Shown as circles, these elements highlight variables that are not fully predictable or controllable.
• Outcomes: Represented as diamonds, these show the results of interactions between decisions and uncertainties.
• Influence Arrows: Arrows connect variables to show directional influence, illustrating cause-effect or dependency relationships.

Why Use Influence Diagrams?

Influence Diagrams help stakeholders and safety professionals:

• Map complex systems in a simplified, visual format.
• Identify the underlying causes of OH&S risks.
• Clarify stakeholder impact on outcomes, decisions, or safety policies.
• Improve risk-based thinking in safety strategies, as encouraged in ISO 45001 Clause 6.1.

Unlike linear tools like flowcharts or decision trees, Influence Diagrams emphasise probabilistic relationships and interdependencies, making them ideal for addressing uncertainties in operational safety, stakeholder engagement, and regulatory planning.

Application Example: OH&S Stakeholder Impact

In an ISO 45001 implementation project, an Influence Diagram can be used to map how worker feedback (uncertainty) affects safety policy design (decision), which in turn impacts incident reduction (outcome). Arrows can trace how indirect stakeholder attitudes or external pressures influence the system’s final performance.