Improving human reliability through the application of Safety Critical Task Analysis (SCTA) identifies steps within a work task where human failure may result in undesired outcomes, both safety and performance related. It then examines the characteristics of the failure, the performance shaping factors which may contribute to the likelihood of the failure occurring and develops additional design controls to either prevent the human failure and / or mitigate against the consequences if it occurs.

Systematic Human Error Reduction and Prediction Approach (SHERPA) is a common means to conduct SCTA. On completion there is a simple table from which a concise report with clear recommendations is produced.

There are four key steps to the SHERPA methodology:

1. Task Analysis – This involves a review of the relevant work documentation (procedures, work instructions etc) to map the task steps, where human failure may occur, against the hazards which require improved controls (these become the steps included in the analysis). This is generally done as a desktop activity first then validated with relevant Subject Matter Experts (SME) for the task.
2. Identify Failure Types – This activity assesses each task step of interest for the types of failure which could occur and the associated consequences. This also is generally done as a desktop review initially and validated with relevant SMEs and end users during execution of the task in the field.
3. Identify Performance Shaping Factors (PSF) – These are the factors which may increase the likelihood of the error occurring. A first pass can be attempted as a desk top review however in field analysis of the task and consultation with the end user is critical to identify and understand PSFs.
4. Analysis of Existing Control Measures – This examines the effectiveness of exiting risk management measures to control against the PSF’s identified for each potential human failure. From the findings, additional design and administrative controls are provided for inclusion in the task resulting in more effective prevention of human failure and mitigation of consequences if it occurs.

SCTA’s are commonly conducted in three ways to developed improved design and administrative controls (from most effective to lease effective):

1. During Human Factors Engineering activities in the project lifecycle;
2. During existing operations; and
3. In response to incidents.