Training Work Processes Workforce

Does Your Human Reliability Measure Up?

Klaus M. Blache | June 1, 2021

Can your human-reliability be improved by addressing NASA’s “Dirty Dozen” list of most frequently observed people issues?

Organizations focused on improving the reliability and maintainability of assets and processes will not realize success without also developing excellence in human reliability.

By human reliability, I’m referring to integrity (willingness to follow standardized procedures, properly close out work orders, and accurately enter data), focus on improving plant-floor practices, reducing human error, and optimizing the person-work practices interface.

J. Reason and A. Hobbs (Managing Maintenance Error, Ashgate Publishing, 2003) identified numerous physiological and psychological factors that contribute to human error. Examples include poor attention span, work complexity and related distractions, fatigue; stress; decision-making biases; confirmation bias—where we seek information that confirms our initial (and often incorrect) diagnosis of a problem, and emotional decision making—if a situation keeps frustrating us, then we tend to move into “aggressive” mode, often clouding our better judgment.

Human reliability is also affected by poorly written maintenance instructions, old maintenance manuals, poor work layouts, improper tools and techniques, and poor machinery and equipment design.

Various studies show that more than 50% of all equipment failures are the result of a maintenance intervention. Because of the items mentioned above, there are incorrect identification of information, problems not detected, memory failures, memory lapse, lack of training/skills, and not following the task procedure.

It’s generally accepted that 80% of maintenance errors involve human factors. As reported by NASA’s Office of Safety and Mission Assurance Human Factors Program, (, the “Dirty Dozen” list depicts the most frequently observed human-related issues discovered during Fiscal Year 2019 agency-mishap and close-call investigations. These issues contributed to more than $3.2 million in damage costs and at least 546 workdays of lost time:

Decision-making: When decisions don’t go as taught or intended, resulting in an unsafe situation.

Communication: Communication breakdowns are involved in most all mishaps.

Technical environment: When technological tools fail to perform or underperform it creates risks to manage.

Inadequate supervision: Supervisors who don’t provide enough guidance and mentoring put their subordinates at risk.

Psychological conditioning: Mental states alter our interactions in ways that affect successful work operations.

Organizational operation: Policies, processes, and procedures are applied to how organizations conduct business.

Organizational resources: The organization provides tools to conduct business successfully.

Skill-based: Taught patterns of behavior are performed easily and unconsciously over time. When those patterns break down, it creates unsafe situations.

Violation: Routine violations are sanctioned by the organization when coworkers, supervisors, managers, or leaders “look away.”

Supervision-planned inappropriate operation: Supervisors who plan inappropriate work (not a violation) put their colleagues and mission at risk.

Supervisory violation: Supervisory violations create dangerous conditions. The mission impact is greater because it affects more people in the organization.

Organizational culture/climate: This is the working atmosphere within the organization, e.g., culture, climate, morale).

As you have no doubt concluded, improving safety and reducing human error is highly interconnected with good human factors and design for maintainability practices. Instill maintenance human reliability and ergonomics to assure that your processes work to maintain excellent asset health. EP

Based in Knoxville, Klaus M. Blache is director of the Reliability & Maintainability Center at the Univ. of Tennessee, and a research professor in the College of Engineering. Contact him at



Klaus M. Blache

Sign up for insights, trends, & developments in
  • Machinery Solutions
  • Maintenance & Reliability Solutions
  • Energy Efficiency
Return to top