Reliability for Life / Reliability 4 Life (R4L)

Written by:  Craig Clapper PE and Tami Strong RN
Published:  February 7, 2023

Human life is a wonderous thing – every human life should be led in abundance. Sadly, into every life some rain does fall. Loss events cut short many human lives. Some who were involved in loss events continue on with guilt and pain, their life diminished by the loss event. More often, smaller loss events in our daily work lives limit our potential to produce – three hours of word processing lost by poor file management, a day’s production contaminated with bacteria and sent to waste, poor situational awareness trips a gas turbine, or a lapse in scheduling leads to a missed presentation and a lost client. Hopefully no one lost their job. Sometimes people do.

Human reliability has the potential to reduce these loss events by 80% every improvement cycle time. Read more about this 80% capability in Chong Chiu1 and Thomas Krause2. Human reliability also has very broad applicability in that better reliability improves safety, quality, user experience, and productivity. And the people who practice skills to achieve high levels of human reliability practice those skills at work and at home and in all the places in between. Better to stay ready than to have to get ready.

Our Reliability 4 Life Group (R4L) is dedicated to reliability for life. Human reliability could and should be harnessed to improve safety to save lives - and to improve quality for better lives and to improve user experience to enrichen those lives. And we are dedicated to using human reliability in all of life’s spaces – where we work, live, learn, and play. And we are also dedicated to using human reliability throughout life. Why limit the goodness to just our work life as an adult? Age-appropriate life skills should be learned and practiced as a child, a young adult, an adult, and as a professional adult.3

Reliability is an emergent property of socio-technical systems (systems in which people perform activities using methods and machines). The reliability equation is shown inset below. Reliability is the probability that the system will perform satisfactorily. So, reliability is the total number of demands minus the few times the system does NOT work (called the system error).

The Reliability Equation

The Reliability Equation

If we try 100 times and are successful 98 times, the reliability is 98% and the system error is 2%. If we increase the reliability to 99% then the system error is reduced to 1%. Percentages work well for everyday living. When describing systems of safety, the system error much smaller and scientific notation is best. For example: what is the probability one would die in a car accident? According to NHTSA statistics the probability of dying in a car crash is 0.000001% per mile driven. Better to write 10-8 per mile driven, which sounds safe until you realize the average driver travels 14,000 miles per year making the probability of dying in a car crash 10-4 per driving year.

Some say the people who practice human reliability are using error prevention skills. This is a bad description which creates a poor mental model. Those practicing human reliability skills increase reliability which crowds-out the system-caused human error. Saying “using error prevention skills” gives the wrong impression that the skill is only used occasionally to stop one of the those few human errors. A better mental model is the skill is used every time the skill is indicated (by an error prone condition) which increases reliability thereby reducing the numbers of error. This can be seen in the figure below.

Reliability Increasing and System Error Decreasing

Increasing reliability decreasing error

Reliability (the teal arrows as bars) increases with each improvement cycle. (An improvement cycle can be short such as the time for habit formation for one person or as long as the time for culture transformation in a large organization.) Since reliability plus system error always add-up to 100%, as the reliability increases – the system error decreases. Reliability puts the squeeze on error.

Some practioners call human reliability skills non-technical skills.4 At Reliability 4 Life, we call them Life Skills because these human reliability skills save life, make life better, and are used throughout one’s life. Please join us on your own high reliability journey by practicing Life Skills as you progress through your life in all of your life spaces – where we work, live, learn, and play. You will be the squeeze on human error and live your life in abundance.



  1. Read about Chong Chiu in Zero Harm by C Clapper, J Merlino, and C Stockmeier (2019)
  2. Read about Tom Krause in Leading with Safety by Thomas Krause (2005)
  3. Life Skills should be learned by all age groups using age-appropriate education and training just as we learn math skills. There is no one year in which to learn all of math. Kindergartners learn to count, first graders learn addition and subtraction, four graders learn division, eight graders learn algebra, and so on. Each new skill increases ability while sustaining skills learned earlier. The best method to sustain the skills is to advance the skills.
  4. Non-technical skill is the best name to use for human reliability when searching the literature.

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