Bow-Tie Analysis

The picture looks like a bow tie. The knot is the event you worry about, such as a major data leak or a chemical release. On the left are the threats that could cause it, with barriers drawn between each threat and the event. On the right are the possible consequences, with barriers that limit the damage. Teams build it in a workshop, which makes gaps visible: a threat with no barrier, or a barrier that depends on one person. It began in high-hazard industries such as oil and gas and aviation and now appears in banks, hospitals and technology firms. It combines ideas from fault trees and event trees in one view. Executives get a one-page view of where a single missing barrier could turn a threat into real harm.

A hospital picks wrong-site surgery as the central event. On the left, threats include a mislabelled scan and a rushed theatre list, each with a barrier such as a pre-operation check. On the right, consequences include patient harm, with barriers such as rapid escalation. The workshop finds one threat with no barrier at all.