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Is the 20th Century HSE Safety Triangle Valid Today?

By Avetta Marketing
April 14, 2020
6 minutes
Is the 20th Century HSE Safety Triangle Valid Today?

Understanding Heinrich's Triangle in the 21st Century

Heinrich’s Triangle (often called the HSE Safety Triangle) is a theory brought forth by Herbert William Heinrich in the early 1930s. Heinrich is considered a pioneer of workplace safety because of his research into and writings about industrial accident prevention, but does his theory still hold up almost a century later? Do his conclusions still apply to today’s workforce? 

According to many experts, no. While there are some redeeming qualities to his work, there is a lot of criticism of his reported data, safety hierarchy triangle, safety ratio, and even his basic principles.  

Let’s examine each of these individually to see if there are any lessons we can still apply almost 100 years later.

The History

Before we begin with the triangle itself, it can help to have some context. First of all, in the 1920s there was great resistance so any sort of “standard” or “regulation” against businesses. The government was not welcome to intervene in any way to make workplaces safer. Labor conditions were deplorable and grueling, and injuries and death were common. 

In 1913, the U.S. Bureau of Labor Statistics documented a rate of 61 deaths per 100,000 workers. By the early 1930s, when Heinrich published his famous book “Industrial Accident Prevention: A Scientific Approach” the conditions were just beginning to improve. Worker deaths dropped to 37 deaths per 100,000.

The drop in deaths is attributed to having become more conscious and focused on safe working conditions. However, the emphasis on these was placed on the individual worker, not the unsafe working conditions or processes. 

Another important thing to note is that Herbert Heinrich did his research and wrote his book while working as an assistant superintendent in the Engineering and Inspection Division of an insurance company. This brings into question his motives behind the research.

Now that we know a bit of the history, let’s delve into the triangle itself. 

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What Is the HSE Safety Triangle?

The HSE Safety Triangle is a graphic that depicts the hierarchy of workplace accidents:

  • The bottom, widest section of the triangle signifies Unsafe Acts 

  • Above that, Near Misses 

  • Next is Minor Injuries

  • Followed by Lost Time Injuries 

  • and Fatality 

The wider the base (Unsafe Acts), the wider the peak (Fatality). 

This pyramid theory puts the emphasis on unsafe acts, rather than unsafe conditions, processes, or designs. In essence, it places all fault on the individual actions of individual workers and does not put any blame on managers, company culture, or the system. 

The Heinrich Triangle Ratio 

In his book, Heinrich puts forth a specific ratio of 330-300-29-1. Here’s what these numbers mean:

  • In a group of 330 accidents

  • 300 will result in no injuries

  • 29 will result in a minor injury

  • 1 will result in a major injury

This domino theory has historically drawn many followers, but recently there have been many more critics questioning its validity. 

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Bad Data and Poor Basic Principles

To come up with his pyramid and ratio, Heinrich reviewed 75,000 injury and illness cases from insurance records and plant managers. While these records are important, we should note that they all came from the point of view of those who would have typically had the most to lose if an accident wasn’t listed as showing the worker at fault. 

From these reports, Heinrich believed that “the occurrence of an injury invariably results from a completed sequence of factors”: 

  1. Ancestry and social environment

  2. Fault of person

  3. Unsafe act or mechanical or physical hazard

  4. The accident

  5. The injury

What he is saying is that an unsafe act, fault of a person, or the worker’s personal culture are solely to blame for injury in the workplace. This thought completely exonerates a process or company from any liability to its workers for unsafe cultures, practices, tools, and systems. 

Does the HSE Safety Triangle Still Apply Today?

Knowing all this background information, is there any way the HSE Safety Triangle still applies today in our modern, strictly regulated industries? Surprisingly, yes! 

While there are now comprehensive investigations that go into injury reporting, constant upgrades in processes and systems, and a much broader culture of safety in general than there ever were in Heinrich’s day, we can still thank him for getting the ball rolling. Before his time, no one had taken a second look at the safety of workers. He put that need into the spotlight and built the foundation for improvements moving forward. And now, worker fatality rates have gone as low as 3.5 per 100,000. 

Let’s look at Heinrich’s five factors and apply them to today’s standards and expectations to see what we can learn:

  1. Both personal culture and company culture contribute to a safe environment.

  2. When an individual gets hurt, we figure out what in the design or process failed or allowed it to happen.

  3. Both unsafe acts and unsafe conditions need to be managed.

  4. Safety should not compete against production. They should work hand-in-hand.

  5. Commitment isn’t enough. There must be action.

In the end, and even with the shortcomings of his findings and conclusions, Heinrich should certainly be credited for creating a starting point to safety that did not exist before his time. He should also be thanked for stating that, 

“Management has the best opportunity and ability to prevent accident occurrence, and therefore should assume the responsibility.” 

 Learn more about Avetta's commitment to safety and health

For more information about Avetta's Contractor Management software, Contractor Prequalification or Supply Chain Risk Management, visit, email [email protected] or call 844.633.3801.

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