SMS Tools


Human Reliability Analysis

HRA is a technique used to predict the possible errors that may occur in terms of human factors and the contributing human role, during a task and to identify error recovery possibilities. It aids to find remedial strategies to eliminate the causes and enhance the likelihood of recovery before consequences. It can also be used in accident analysis to identify contributing factors and suggest recoveries.

The HRA can be used Predictively as follow:

  • Preconditioned Plan Analysis: identifies errors in planning stage of task conditions
  • Embedded Plan Analysis: identifies errors of plan specifying steps as per conditions
  • Task Element Analysis: identifies errors at each step

The errors can be classified as: Action error/ Checking error/ Retrieval error/ Transmission error/ Selection error/ Planning error

HRA is essential for critical systems as all the credible errors are identified. It provides standardisation setting up the basis for consistency. It can improve design by early identification during the planning/ design stage. It requires however, a substantial investment in time and effort, as well as deep knowledge of the system and its operation.

The following HRA tools are available:

  • THERP – Technique for Human Error Rate Prediction
  • HEART – Human Error Assessment & Reduction Technique
  • SLIM – Success Likelihood Index Methodology
  • THETA – Top-Down Human Error & Task Analysis