Course 700 - Introduction to Safety Management

Element 6: Accident Investigation

Fix the System, Not the Blame

Incidents vs. Accidents
Incidents vs. Accidents

Incident and accident investigation is an important element in a safety management system. We encourage you to investigate all incidents and accidents in the workplace to fix the system, not the blame. We will emphasize this critical point repeatedly.

Effective investigations are conducted by a mix of supervisors, managers, and employees working together because they bring more knowledge, understanding, and unique perspectives to the process. This module will cover the basics of conducting incident and accident investigations.

Incidents and Accidents Defined

OSHA does not use the term "accident;" however, we believe it's important to clarify the distinction between an incident and an accident. Therefore, we use the following definitions for these two terms in our training:

  • Incidents are events that do not result in an injury or illness. Incidents are also called "near-misses" or "near-hits."
  • Accidents are unexpected, unplanned events that result in some kind of injury or illness to employees. Accident are also called "mishaps."

Click on the button to see more differences in characteristics between incidents and accidents.

What's the difference?


  • can be negative (unwanted) or positive (wanted);
  • do not result in injuries, or illnesses
  • may or may not result in property damage;
  • may be a planned or unplanned;
  • may be intentional or unintentional;
  • may or may not be due to error; and
  • are not always accidents.


  • are always considered negative (unwanted);
  • result in injuries, illnesses, and possibly property damage;
  • are always unplanned;
  • are unintentional;
  • are due to some kind of error; and
  • are always incidents.

1. In the context of occupational safety, what is the difference between an incident and an accident?

a. Incidents are always planned, but accidents are always unplanned
b. Accidents are always incidents, but incidents are not always accidents
c. Incidents are always negative (unwanted), but accidents are not
d. Both incidents and accidents may cause injuries

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The Accident Investigation Process

Fix the system, not the blame.
Fix the system, not the blame.
(Click to enlarge)

Accident investigation is an important process to identify and control hazardous conditions, influence employee behaviors and improve system weaknesses that result in workplace accidents. We'll say it again because it's so important: the purpose of an investigation is to fix the system, not the blame. The various concepts, principles, and procedures in the investigation process will help you transform your workplace into an accident-free zone. But first, you should develop a systematic step-by-step process.

Steps in the Accident Investigation

Click on the button to see typical steps in the accident investigation process.

Your accident investigation should be conducted systematically using the following steps:

  1. Secure and document the accident scene
  2. Interview witnesses
  3. Construct a sequence of events
  4. Conduct cause analysis
  5. Develop solutions
  6. Write the report

Many factors cause or contribute to an accident. What's the point? Explaining why an accident occurred is not always an easy task. It requires careful analysis using a systematic process like the one we discussed above. The investigator must also understand that, most likely, there are root causes for the accident.

2. What is the primary purpose of an accident investigation?

a. To fix the system, not the blame
b. To identify unsafe employee behaviors
c. To establish blame so we can fix the system
d. To discover relevant conditions and behaviors

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Plan The Work - Work The Plan!

Be ready to investigate.
Be ready to investigate.

When a serious accident occurs in the workplace, everyone will be too busy dealing with the emergency at hand to worry about putting together an accident response and investigation plan, so the best time to develop the plan and its procedures is before the accident occurs.

The accident response and investigation plan should include as a minimum procedures to:

  • notify company supervisors and managers that an accident has occurred;
  • notify outside agencies (fire, EMTs, police, OSHA, etc.) that an accident has occurred;
  • appoint employees, supervisors, and managers who will conduct accident investigation;
  • instruct and train accident response and investigation procedures to responders, investigators, supervisors, and managers;
  • conduct accident investigation corrective actions; and
  • reviewing, analyzing, and improving accident investigation procedures.

3. Who should conduct an accident investigation?

a. The safety committee
b. Employees, supervisors, and managers
c. The safety manager
d. Only third parties

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Accidents Just Happen...Don't They?

Many near-miss incidents reveal there are still safety issues that need to be fixed.
These ratios are valid only in large samples.

If a company has 20 disabling injuries one year, and sets an objective to reduce the accident rate by 50% by the end of the next year, aren't they planning to have ten accidents for that year? If they reach that goal, won't they be happy and content? They might say, "Hey, let's kick our feet up, pat ourselves on the back, and relax!" Is that acceptable? Of course not — you can't afford to relax or be content in your safety performance.

Severity - Just a Matter of Luck

Historically, safety professionals have been told that for every fatality, there will be a greater number of serious injuries, an even higher number of minor injuries, and even more near misses. While these ratios might be true for large samples, you should not assume they are valid for small samples within one company. Do not assume that if you reduce the number of minor injuries, you will automatically reduce the number of serious injuries. It doesn't work because the severity of an injury is more a function of luck than ratios.

For instance, if five painters fall off the same ladder at different times throughout the year, the severity of the injury each painter suffers will depend on their orientation when they impact the surface: and that's the result of any number of variables. Every one of the five falls might result in a serious injury. On the other hand, they might all result in no injury. It's not the number of falls that determines the nature of the injuries: it's the unique variables inherent in each fall - and that depends on just plain luck — a roll of the dice.

4. More than anything else, what does the severity of an injury depend on?

a. The age of the worker being injured
b. Just plain luck
c. The type of accident that occurs
d. The number of times a given accident occurs

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Accident Scenario

First, you must secure the accident scene.
Secure the accident scene first.
(Click to enlarge)

You've just been notified of an injury in the workplace and immediately swing into action. You grab your investigator's kit and hurry to the accident scene. By the time you get there, the Emergency Medical Team (EMT) is administering first aid. It's a serious accident, so the victim is transported to the hospital. Now it's safe to investigate.

Secure the Scene

The first task after you arrive is to secure the accident scene, but don't start until it's safe to do so. And, you don't want to get in the way of emergency responders. The easiest way to do this is to place yellow warning tape around the area. If security tape is not available, warning signs or guards may be required. Make sure others do not remove because you'll take photos and measurements later.

Remember, at the request of OSHA, the employer must mark for identification, materials, tools, or equipment necessary to the proper investigation of an accident. Material evidence mustn't somehow get lost or "walk off" the scene.

5. What is the first thing that needs to happen before investigating an accident at work?

a. Start writing an accident report
b. Send all workers home
c. Secure the scene
d. Nothing, leave the scene alone

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Gathering the Facts

The next step in the procedure is to gather useful information about what directly and indirectly contributed to the accident.


Interviewing eyewitnesses to the accident is the most important and effective method to gathering factual information about what happened in an accident. Click on the button to see important points to remember about the interview process.

Effective interviewing techniques include the following:

  • Take initial statements from eyewitnesses and others. They can give you a lot of information about the accident.
  • Thank the interviewee for participating, let them know the interview is confidential, and that it is not being conducted to place blame.
  • Convey that the purpose of the interview is to determine the facts that ultimately lead to the root causes.
  • Let them know that you may conduct follow-up interviews if more questions surface.
  • Interview other interested persons such as supervisors, co-workers, etc., to get the facts related to training, supervision, and resources.

Other Methods

In addition to interviewing eyewitnesses to determine what happened, it's important to document. Click the button to see other methods you can use to document the accident scene.

Accident Investigation Tools
Systematically gather the facts about the accident.

Additional accident investigation tools include the following:

  • Take photographs: A picture is worth a thousand words.
  • Take measurements: Helps to know distance and position of objects.
  • Draw sketches: Identifies and locates objects and shows motion through time.
  • Make observation: Look at the scene from different locations.
  • Review records: Previous accident reports, training records, JHAs, etc.

You should also review records associated with the accident. Click the button to see records to check during your investigation.

Records to Review

Accident Investigation Tools
Thoroughly review records.
  • Training records
  • Disciplinary records
  • Medical records (as allowed)
  • Maintenance records
  • EMT reports
  • Police reports (rare)
  • Coroner's report (fatalities)
  • OSHA 300 Log (past similar injuries)
  • Safety Committee records

Remember you are gathering information to use in developing a sequence of steps that lead up to the accident. You are ultimately trying to determine surface and root causes for the accident. It is not your job, as an accident investigator, to place blame. Just gather the facts.

6. What is the most important method to find out what happened in a workplace accident?

a. Taking photographs of the scene
b. Interviewing eyewitnesses
c. Including measurements
d. Observing the scene

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Determine the Sequence of Events

Like dominoes, an accident is the final event in a sequence of events.
Each event describes one actor and one action.

Now you've gathered tons of information about the accident, and it's piled high on your desk. What do you do with it? You must read through the facts gathered in your investigation to develop an accurate sequence of events that contribute to and include the actual injury event.

Actor and Action

Each event describes an actor (a person or thing that does something) and an action (what the person or thing does).

An event might state, "Employee #1 stands on the top rung of the ladder." In this example, "Employee #1" is the actor, and "stands on the top rung of the ladder" is the action.

Click the button to see an example of a sequence of events the would be constructed during an investigation.

Sample Sequence of Events

Understanding the sequence of events leading up to an accident is very important. The following sequence of events is based on a real-life accident that resulted in the death of an employee.

  1. Employee #1 returned to work from lunch at 12:30 p.m.
  2. At approximately 12:45 p.m., employee #1 picked up a 15-foot irrigation pipe.
  3. Employee #1 oriented the irrigation pipe vertically.
  4. The pipe contacted a sagging high voltage power line running directly over the work area.
  5. When the pipe contacted the powerline, a lethal surge of electrical current electrocuted Employee #1.
  6. Employee #2 heard a "zap" and a "flash."
  7. Employee #2 turned to see employee #1 falling to the ground.
  8. Employee #2 attempted to awaken Employee #1.
  9. Employee #1 did not respond to Employee #2's attempt.
  10. At 12:50 p.m., employee #2 called 911 and requested immediate EMT help.
  11. At about 12:55 p.m., paramedics arrived.
  12. The paramedics immediately began treatment in an attempt to stabilize employee #1.
  13. At about 1:10 p.m., an ambulance arrived to transport Employee #1 to the hospital.
  14. Hospital emergency room doctors pronounced Employee #1 dead at 1:30 p.m. Cause of death was electrocution.

You can read more about constructing the sequence of events in OSHAcademy Courses 162, Accident Investigation Basic, and 702, Effective Accident Investigation.

7. What should each event in the accident sequence of events include?

a. The duration of the event
b. Identification of the person at fault
c. Conditions and practices
d. An actor and an action

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Determine the Causes

Always look for root causes for hazards and exposure.
You're not done until you dig up the roots.

After developing the sequences of events, the next step is to determine surface causes. This step may be difficult because you are first searching for the accident's surface causes in each step, which can take some time. From the clues you uncovered during this phase of the analysis, you'll be able to determine the system weaknesses or root causes.

Refer to the "accident weed" to the right.

Surface Causes. — are represented by leaves on the weed. They are the unique hazardous conditions and individual unsafe or inappropriate behaviors. There are two categories of surface causes: primary and secondary.

  • Primary surface causes are the immediate unique conditions or individual behaviors that cause accidents. Examples of unique primary surface causes of accidents include:
    • an unguarded grinder
    • a defective respirator
    • a floor hole
  • Contributing surface causes are the unique conditions and behaviors that indirectly contribute to, but do not cause the accident. Unique contributing surface causes include:
    • removing the guard on a grinder
    • failure to test a respirator
    • a hole in the floor is not properly covered

Root Causes. — are represented by the roots of the weed. Root causes pre-exist the surface causes of accidents. They contribute to the unique hazardous conditions and unsafe work practices. Remember, the performance of a safety management system is a function of its design. Therefore, analyze the following two categories of root causes: design and performance.

  • Design root causes are those SMS policies, programs, plans, processes, and procedures that are missing or inadequately designed. For instance, if training does not include using PPE, the SMS is not properly designed. System root cause design weaknesses include:
    • supervisors and managers do not have written safety responsibilities
    • a formal safety training plan does not exist
    • no formal scheduled safety inspection plan or procedures
  • Performance root causes are management actions (behaviors) that somehow contribute to accidents. For example, when supervisors fail to conduct safety inspections, the performance of the SMS is flawed. System root cause performance weaknesses include:
    • failure of supervisors and managers to perform their safety responsibilities
    • safety orientation, initial training, or retraining is not being conducted
    • supervisors, employees, and safety committees are not conducting safety inspections

8. Supervisors failing to regularly conduct scheduled safety inspections would be considered a _____.

a. primary surface cause
b. contributing surface cause
c. performance root cause
d. design root cause

Next Section

The Accident Report

Recommend corrective actions and system improvements.
Recommend corrective actions and system improvements.
(Click to enlarge)

Now that you have developed the sequence of steps leading up to and including the accident and determined the surface and root causes, it's time to report your findings and make recommendations for corrective action.

Most companies purchase accident investigation forms. That's fine, but some forms leave little room to write the type of detailed report necessary for a serious accident. If you use a form, make sure you attach important information like the sequence of events and findings, including surface and root causes.

A better idea is to develop your own report form that includes the following five sections:

Section One - Background Information: This is the who, what, where, when, why,etc. It merely tells who conducted the inspection, when they did it, and who the victim was.

Section Two - Description of the Accident: This section includes the sequence of events you developed. Just take the numbers off and make a nice concise paragraph describing the events leading up to, including the accident.

Section Three - Findings: This section includes a description of the surface and root causes associated with the accident. List the surface causes first and then their associated root causes. Remember, your investigation is to determine the causes, not blame. It's virtually impossible to blame an individual for a workplace accident. Don't let anyone pressure you into placing blame in the report.

Section Four - Recommendations: This section may be part of your report if requested by your employer. Recommendations should relate directly to the surface and root causes of the accident.

It's crucial that, after making recommendations to eliminate or reduce the surface causes, you use the same procedure to recommend actions to correct the root causes. If you fail to do this, it's a sure bet that similar accidents will continue to occur.

Section Five - Summary: In this final section, it's important to present a cost-benefit analysis. The decision-maker should know the total accident costs and the benefits of taking corrective action. The total costs would be the potential future direct and indirect costs if a similar accident were to occur. Compare the total accident costs with the investment in taking corrective actions.

9. What will happen if you fail to correct the root causes of an accident?

a. Similar accidents will occur
b. Employees will thank you for it
c. The company will save money
d. You won't discover who was at fault

Check your Work

Read the material in each section to find the correct answer to each quiz question. After answering all the questions, click on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.


Kate's Story - A Safety Video

"Kate's Story" is a video produced internally by Jacobs that tells the tragic story of Jacobs employee Kate Carpenter (London, UK), whose husband, John Kinns, also an employee, lost his life as the result of injuries sustained in the field. The video has been shown and discussed at office meetings across the globe and has had a profound impact.

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