Bowtie diagrams: A user-friendly risk communication tool

The rail infrastructure controller in Great Britain recognised that more work was required to allow a robust and consistent demonstration that appropriate health and safety risk assessments are being undertaken throughout each stage of the contracting process. In response to this requirement, the authors were engaged to assist the rail infrastructure client with the development of a new risk-based contractor management and assurance process. Bowtie diagrams were selected as a key component of this process to represent:

Key safety risks associated with rail construction projects;

Potential causes and consequences of unwanted events;

Good practice in risk barriers/controls.

To test the suitability of Bowties for risk communication to contractors, three key hazards were identified for Bowtie analysis. These and the specific top events selected were as follows:

Hazard: Working at height – from scaffold, ladders, mobile elevating working platforms, mobile towers or ledges;

Top event: Falls from height – to surface;

Hazard: Working in vicinity of uninsulated conductors and supply points;

Top event: Contact with live/charged equipment >60 V;

Hazard: Working on or near the line;

Top event: Personnel in path of oncoming train.

A one-day Bowtie development workshop was held for each of the hazards selected. These were attended by client personnel with the required knowledge and expertise of the hazard and associated barrier measures, ensuring the necessary levels of input and consultation.

Feedback to date on the Bowtie approach has been positive, both within the client and contractor organisations. Bowties provide a method of communicating the client’s expectations about levels of protection to infrastructure project contractors and address the following key requirements:

Allow contractors to understand risk management requirements in detail and to price jobs accordingly;

Enable identification of gaps in the barrier of key risks and facilitate implementation of best practice;

Can be used by the client as a project safety assurance tool to check the risk management measures in place against those defined in the Bowtie;

Demonstrate to the regulator that the client is communicating a clear ‘safety story’ throughout a project.

This paper describes the Bowtie development process in accordance with Ten Golden Rules including how human factors can be incorporated in a systematic and meaningful way. It will demonstrate how the Bowties developed within this project represent in a clear and accessible manner what constitutes industry best practice with regard to controlling important safety risks in construction projects.