Engineers are required to make decisions about a variety of different topics in the building design process from interpreting prescriptive code requirement, probabilistic risk assessments, and modelling (e.g. fire/evacuation/structural modelling). The decision-making process can be based on well-defined deterministic mechanisms for selection of outcomes or, conversely, defer to the judgement of the engineer to determine a suitable outcome. In situations when an engineer is required to exercise their own judgement, they will draw on their own professional experience possibly being informed by use of analytical/computational tools to come to a conclusion regarding a suitable outcome. This process may also be influenced by various other factors such as cognitive biases and personal factors to the engineer e.g. past experience, boredom, fatigue, illness, etc. which may contribute to variation in the outcomes to decision-making. Different engineers may determine different outcomes to the same decision which may all be within the bounds of acceptable validity for a given application. However, due to each building typically only being designed and/or decisions only being posed to a single engineer once, most building design projects will never have the opportunity to highlight potential variation caused by exercising professional judgement. Design teams or approving authorities may never become aware of such variability unless they have worked on past identical/similar projects or the design is entirely reviewed by another engineer. This variability (which can be referred to as 'Noise') can cause added time to a project and/or additional costs in associated unnecessary requirements/changes to building designs without stakeholders being aware. It is therefore desirable to mitigate unwanted variability and introduce consistency where engineers are required to exercise judgement whilst at the same time provide sufficient flexibility to design teams in the building design process. This study is intended to begin to address these issues by identifying where unwanted variability may occur within fire engineering in different contexts which require engineers to exercise professional judgement in the building design process. The discipline of fire engineering has been chosen as a focus for the study however, the findings are expected to be broadly applicable to other engineering disciplines, particularly within the building design process.
A survey was conducted which identified and measured the extent variability can occur in different contexts within fire engineering. This includes decision-making regarding the use of prescriptive fire codes, probabilistic risk assessments, calculations, and evacuation modelling. Results from the survey highlight variability is influenced by the context in which decisions are made, the level of required determinism to be followed within a decision framework, and the provision of bounding criteria in a given decision. Results from the analysis can inform fire engineers and stakeholder expectation regarding potential variability in associated decision-making within each context. Methods to identify and reduce unwanted variability are then presented to improve decision-making. The study may be of use to not only fire engineers, but any engineer involved in the building design process.