Kevin Ian Schmidt

Causal Tree Analysis Root Cause

An accident may be the result of many factors (simultaneous, interconnected, cross-linked events) that have interacted in some dynamic way. In an effective accident investigation, the investigator will conduct three levels of root cause analysis:

  • Injury analysis: At this level of analysis, we do not attempt to determine what caused the accident, but rather we focus on trying to determine how harmful energy transfer caused the injury. Remember, the outcome of the accident process is an injury.
  • Surface Cause Analysis: Here you determine the hazardous conditions and unsafe behaviors described in the sequence of events that dynamically interact to produce the accident. The hazardous conditions and unsafe behaviors uncovered are the surface causes for the accident and give clues that point to possible system weaknesses.
  • Root cause analysis: At this level, you’re analyzing the weaknesses in the safety management system that contributed to the accident. You can usually uncover weaknesses related to inadequate safety policies, programs, plans, processes, or procedures. Root causes always pre-exist surface causes and may function through poor component design to allow, promote, encourage, or even require systems that result in hazardous conditions and unsafe behaviors. This level of investigation is also called “common cause” analysis (in quality terms) because you’re identifying a system component that may contribute to common conditions and behaviors that exist or occur throughout the company.

Injury Analysis

It’s important to understand that all injuries to workers are caused by one thing: the harmful transfer of energy. Let’s take a look at some examples that illustrate this important principle.

  • If a harsh acid splashes on your face, you may suffer a chemical burn because your skin has been exposed to a chemical form of energy that destroys tissue. In this instance, the direct cause of the injury is a harmful chemical reaction. The related surface causes might be the acidic nature of the chemical (condition) and working without proper face protection (unsafe behavior).
  • If your workload is too strenuous, force requirements on your body may cause a muscle strain. Here, the direct cause of injury is a harmful level of kinetic energy (energy resulting from motion), causing injury to muscle tissue. A related surface cause of the accident might be fatigue (hazardous condition) or improper lifting techniques (unsafe behavior).

The important point to remember here is that the “direct cause” of the injury is not the same as the “surface cause” of the accident event.

  • The direct cause of injury is the harmful transfer of energy as a consequence of your exposure to that energy. The direct result of the harmful energy transfer is injury. The cause is the harmful transfer of energy. The effect is the injury.
  • The surface cause of the accident is the condition and behavior that interacts in a way that results in the harmful transfer of energy. The interaction of the condition and behavior is the cause. The effect is the harmful transfer of energy.

Harmful Forms of Energy

  1. ACOUSTIC ENERGY – Excessive noise and vibration.
  2. CHEMICAL ENERGY – Corrosive, toxic, flammable, or reactive substances. Involves a release of energy ranging from “not violent” to “explosive” and “capable of detonation.”
  3. ELECTRICAL ENERGY – Low voltage (below 440 volts) and high voltage (above 440 volts).
  4. KINETIC (IMPACT) ENERGY – Energy from “things in motion” and “impact,” and are associated with the collision of objects in relative motion to each other. Includes impact between moving objects, moving object against a stationary object, falling objects or persons, flying objects, and flying particles. Also involves movement resulting from hazards of high pressure pneumatic, hydraulic systems.
  5. MECHANICAL ENERGY – Cut, crush, bend, shear, pinch, wrap, pull, and puncture. Such hazards are associated with components that move in circular, transverse (single direction), or reciprocating motion.
  6. POTENTIAL (STORED) ENERGY – Involves “stored energy.” Includes objects that are under pressure, tension, or compression; or objects that attract or repulse one another. Susceptible to sudden unexpected movement. Includes gravity – potential falling objects, potential falls of persons. Includes forces transferred biomechanically to the human body during lifting.
  7. RADIANT ENERGY – Relatively short wavelength energy forms within the electromagnetic spectrum. Includes infra-red, visible, microwave, ultra-violet, x-ray, and ionizing radiation.
  8. THERMAL ENERGY – Excessive heat, extreme cold, sources of flame ignition, flame propagation, and heat related explosions.

What are Surface Causes?

The surface causes of accidents are those hazardous conditions and unsafe or inappropriate behaviors within the sequence of events that have directly caused or contributed in some way to the accident.

Hazardous Conditions

  • Are unique things or objects that are somehow defective or unsafe
  • Are “states of being” such as employee fatigue
  • May also be unique defects in processes, procedures or practices
  • May exist at any level of the organization
  • Are the result of deeper root causes

Hazardous conditions may exist in any of the categories below.

  • Materials
  • Machinery
  • Equipment
  • Tools
  • Chemicals
  • Environment
  • Workstations
  • Facilities
  • People
  • Workload


Unsafe or Inappropriate Behaviors

It’s important to know that most hazardous conditions in the workplace are the result of the unsafe or inappropriate behaviors that produced them.

  • Actions we take or don’t take that increase risk of injury or illness
  • May also be thought to be unique performance errors in a process, procedure or practice
  • May exist at any level of the organization
  • Are the result of deeper root causes

Below are some examples of unsafe or inappropriate employee/manager behaviors.

  • Failing to comply with rules
  • Using unsafe methods
  • Taking shortcuts
  • Horseplay
  • Failing to report injuries
  • Failing to report hazards
  • Allowing unsafe behaviors
  • Failing to train
  • Failing to supervise
  • Failing to correct
  • Scheduling too much work
  • Ignoring worker stress


System Analysis

Let’s take a look at analyzing the surface causes to determine possible safety management system weaknesses. There are many “general” conditions and behaviors (variables) inherent in the safety management system. Oh yes… to me the safety management system is “organic”. By that I mean it is dynamic, ever-changing and behaves as though it were alive. Think about it. If that’s a little too metaphysical for you… read on.

The root cause for an incident is the underlying safety management system weaknesses, which consist of thousands of variables, any number of which can somehow contribute to the surface causes of accidents. These weaknesses can take two forms.

  • System Design Root Causes: Inadequate design of one or more components of the safety management system. The design of safety management system policies, plans, programs, processes, procedures and practices (remember this as the 6-P’s) is very important to make sure appropriate conditions, activities, behaviors, and practices occur consistently throughout the workplace. Ultimately, most surface causes will lead to system design flaws.
  • System Implementation Root Causes: Inadequate implementation of one or more components of the safety management system. After each safety management system component is designed, it must be effectively implemented. You may design an effective safety plan, yet suffer failure because it wasn’t implemented properly. If you effectively implement a poorly written safety plan, you’ll get the same results. In either instance, you’ll eventually need to improve one or more policies, plans, programs, processes, procedures or practices.

Effective Recommendations

An accident investigation is generally thought to be a “reactive” safety process because it is initiated only after an accident has occurred. However, if we propose recommendations that include effective immediate corrective actions and system improvements, we may transform the investigation into a valuable “proactive” process that helps to prevent future injuries. In this module we’ll explore tips and tactics for making effective recommendations that “sell” safety improvements.

Once you have developed engineering and administrative controls to eliminate or reduce injuries, the challenge becomes convincing management to make changes. Management will most likely understand the importance of taking corrective action and readily agree to your ideas. However, if management doesn’t quite understand the benefits, success becomes less likely. Your ability to present effective recommendations becomes all that more important. This module will help you learn how to put together “an offer they can’t refuse,” by emphasizing the long-term bottom-line benefits of the corrective action you are recommending.


Download and view the Causal Tree Analysis Root Cause Training below




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