The Shape and Why It Works

A bow-tie diagram places a top event at the centre, with threats on the left leading to it, and consequences on the right flowing from it. Preventive barriers sit on the left legs; recovery barriers on the right.

The five elements

• Hazard — something with the potential to cause harm that is part of normal operation: hydrocarbon under pressure, a suspended load, traffic on site.
• Top event — the moment control of the hazard is lost. Not yet an accident.
• Threats — what could cause the top event, each its own pathway.
• Consequences — what results once control is lost.
• Barriers — the measures that interrupt a pathway.

Why the shape helps

It shows, on one page, that a single barrier protects against one threat only, and it makes barrier gaps visible to people who do not read risk registers. That communicative power is the main reason bow-ties spread beyond specialists.