The Health and Safety Executive (HSE) uses the MISHAP01 (Model for the estimation of Individual and
Societal risk from HAzards of Pipelines) model to calculate the risks associated with Major Accident Hazard
(MAH) pipelines in Great Britain. The risks calculated are used to determine the distances to land-use
planning (LUP) zones around the MAH pipeline. MISHAP was originally developed in the 1990s using Visual
Basic 6 (VB6). An updated version, MISHAP01, was released in 2001. A Microsoft Excel® application, called
PipelineRiskAT was also developed to allow multiple MISHAP01 runs to be carried out concurrently. HSE
asked the Health and Safety Laboratory (HSL) to rewrite the model, using Microsoft Excel®, to bring the
code up-to-date and to allow easy implementation of improvements to the model. The initial specification
of the code rewrite was to replicate the results obtained from MISHAP01. HSE also asked that the
functionality of MISHAP01 and PipelineRiskAT be consolidated into a single software tool. The revised
model is called MISHAP12. HSL have tested the new code using a representative set of 584 pipelines.
The tests show that there is only a minimal impact on the final LUP zones generated compared to those
generated using the older models.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents,
including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily
reflect HSE policy.

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