Tuesday, April 3, 2012

The Two-Tier Haddon Matrix

An interesting extension and alternative to the Haddon Matrix is suggested by Mazumdar et al. (2007) (http://www.ciop.pl/21107). They are concerned with aiding the understanding and prevention of operational hazards at a large construction site. The standard Haddon Matrix below could be used firstly for analysing a hazard or disaster and, secondly, for identifying how to prevent it – a two-tier structure. In the first matrix, the pre-event consist of risk build-up, the event itself and then the consequences, whilst in the second matrix there would be pre-event risk reduction, event prevention and consequence minimization.

To help understand both these matrices, they also suggest that ‘fish-bone’ diagrams might help to identify and put into context specific actions and behaviours to help understand both how the event happens and how it might be prevented or at least its impact minimized. In some ways this is similar to following a scenario through the Swiss-cheese model outlined in an earlier blog. The higher up the main arrow an action, the earlier on it occurs in the build-up to an event or in the event and post event sequence of actions. Early prevention stops the sequence of events occurring in the first place.

Each of the points made in the fish-bone diagrams and in the matrices can be assigned a reference code that relates that point to a specific event or action. So A1, for example, could be the initial decision of a person to not follow a particular minor safety procedure, A2 is then the event that results because of this, whilst C1 could be supervisory environment that permits such lax practices. This breakdown of events and actions for pre- during and post-event can be carried out along with the associated preventative measures in the second tier of the matrix that would stop these events occurring.

Using this reference code they then build up a cybernetic analysis of the problem (see their paper for the worked example). Leaving aside the mathematical analysis of the relationships the linking together of the events/actions involves, they do provide an alternative way to look at an accident or hazard. The important point is that they identify positive and negative feedback loops in the accident or hazard, the nodes, and are able to link these loops together to form the overall accident or hazard and its outcomes. Using this sort of diagram it is possible to identify how interconnected certain events or actions are; which events or actions provide bridges between feedback loops and which nodes in the network it would most effective to tackle in terms of disrupting or easiest to control the occurrence of the event or hazard.

No comments:

Post a Comment