Useful tools and resources

This page provides access to additional resources to help practitioners understand and use Tripod Beta.

Case studies

Examples of Tripod Beta investigations:

Vehicle rollover in remote desert region (external website)

Chemical plant pipe rupture (external website)

Machine operator cuts hand (external website)

Passenger accident at Brentwood station 28 January 2011 (external website)

Examples of Tripod Beta trees (and frequently made mistakes) in health care (hospitals)

In the medical sector, diagnosis of illness/harm to a patient is often seen as a barrier.  However, technically this is incorrect as a diagnosis in itself it not usually a valid barrier (it fulfills only one of the 'detect, decide, act' functionality of a barrier).  This paper demonstrates some correct ways to deal with issues of using Tripod in the medical sector.

Classifying incident causes

Annex I: Caused by... Leads to... A method for identifying and classifying the underlying causes of incidents, accidents and business losses.   This resource is a companion to the Tripod Beta manual (Annex I).  It provides 11 tables of common preconditions and underlying causes.  These tables can guide the investigator on possible avenues of investigation, the level of depth expected of preconditions and underlying causes, and as a way to classify underlying causes consistently to enable multi-incident analysis.


Incident XP (external website)

  • IncidentXP uses the same software framework as BowTieXP, which makes it possible to link incident analysis results back to the proactive risk assessment diagram. However, IncidentXP can also be used as full-fledged stand-alone incident analysis tool. Includes Tripod Beta.

Tripod Beta tree stencils: PowerPoint presentation (external website)

  • PowerPoint presentation containing blank Tripod Beta tree symbols, to enable you to create Tripod trees without using specialist software. To access, click the 'Tree stencils' tab towards the middle of the page.


A collection of videos to help you understand the theory behind Tripod:

Movie: Explaining Human behaviourHuman Behaviour Theory and Tripod BetaSwiss Cheese Model explainedExplaining Human BehaviourTripod Beta TheoryIntroduction to errors and violationsHow the brain works

Background reading

UK P&I clubwebsite: Tripod theory (external website)

Contains excellent background to human failure and the Tripod theory. Note it uses older terminology (Hazard and Target rather than Agent and Object).

History of the Swiss cheese model (external website)

Shows how the Swiss cheese model has evolved over time.

Selection of incident investigation methods (external website)

October 2009 Loss Prevention Bulletin paper that describes a number of different incident investigation methodologies.  Note that Tripod Beta is the only method that covers 'what happened', 'how it happened' and 'why it happened'.