Accident Investigation

CHAPTER6

The Analytical Process

An accident investigation is the process of breaking down information into pieces until the investigator understands what happened; then he or she can analyze the pieces to determine ways to prevent the accident from recurring. Asking "why" is a crucial first step in discovering the causal factors of an accident.

Causal Analysis

Once the evidence from an accident is gathered, you must discover the accident sequence, and once you know the sequence, causal analysis-the process of determining the causal factors-can begin. (Senecal and Burke 1994) . The goal of causal analysis is to find all of the causes including the systernic causes-not just the immediate or superficial causes. If only the superficial causes are found and dealt with, the same accident could happen again with a different employee.

One of the problems accident investigators sometimes have is knowing ~hen to stop searching for causes. Many accident investigators have used the 5

Whys" technique to find causes. This is simply asking ''Why?" five times to get to the root of a problem. Fo r example, suppose John was working

59

rQU Part JI: Organizing the Investigation

60

d ..nring pipes from one location to another '"h out oors ca ...... ,-- ,, . . vv en a .

c Here are five "Why? questions the investigator c ul Ptpe feU 1oot. · O d a k O!) l·

. d er into the cause of the accident: s Joh •ijs going eep n, each

Investigator: John, why did the pipe fall on your foot?

John: I dropped it.

Investigator: Why did you drop it?

John: It slipped out of my hand.

Investigator: Why did it slip?

John: It was wet. Investigator: Why was it wet?

John: The pipes were sitting in a pool of water.

Investigator: Why were they sitting in water?

John: It rained earlier today.

(Obviously, the questioning process in this case has only begun.)

Causal analysis is a process in which an investigator analyzes, probes discovers, ponders, and uses scenarios, facts, tests, and assumptions t~ determine what caused an accident. Causes and causal factors can exist at many levels-worker, equipment (failure or hazard), supervisor, management, management systems (policies and procedures), and even corporate culture, philosophy, and style. Lower-level causes are usually more specific to one particular accident, but they are still important to list and fix. In fact, problems at the lowest level can lead to worthwhile engineering and equipment corrections that solve a problem or eliminate a hazard. Upper-level causal factors are more difficult to fix, but doing so will affect a broader range of

1 d . . f ·d t (DOE 1999). peop e an s1tuat1ons and help to prevent uture acc1 en s . .

Exhibit 6.1 displays the levels of accountability for accident inve5t1gat1ons.

Causal Analysis Example . ,1 . /. piece~

An accident occurred when a worker did not use a lock and tag to ,so ate 11

equipment and keep the electricity out.

Exhibit 6.1

1• workeror equipment level

2. Supervisor level

3. Management level

4. Corporate level

Chapter 6 : The A na!Jtical Process

LEVELS OF ACCOUNTABILITY

This is the lowest level of accountability. At the worker level work is performed and equipment operates. Causal factors in this area include equipment failures, inadequate training, inexperience, and what many consider human error (which would include training, experience, etc.).

People at this level describe how work is to be done. Causal factors often include inadequate handling of job safety analyses, communication, or scheduling, and lack of proper supervision.

Management level dictates policies and proce- dures. Causal factors at this level are usually related to budget issues, communication, and policies/ procedures. This highest level dictates the culture, philosophy, and style of the company. If problems are found and corrected at this level, many accidents can be prevented.

A lower-level causal factor is that the worker failed to use the proper lockout/ tagout procedure to isolate the energy. A higher-level factor could be that management did not enforce or have a policy on lockout/ tagout. If the lower- level problem is fixed-the worker is trained on lockout/ tagout procedures and given a lock and tag-that worker probably will not have another accident. However, if management develops a policy of training al/workers in lockout/ tagout procedures, many similar accidents can be prevented.

With this type of accident, a causal factor may also exist at the corporate level if upper management failed to audit the plant's procedures and therefore did not find out that the plant lacked lockout/tagout policies. If up~er management started performing policy audits, many more types of accidents d b c • cause y 1ailure to follow policy or procedure-not just electrical andlocko t/ . u tagout acc1dents--could be avoided.

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Part IT: Organi~ng the Investigation

62

This example demonstrates the importance of an 1 . . . a YZJ.ng a all levels. If you mvest1gate only at the lower levels you tn . n accident

th . . ay nuss s at causal factors-and thus e correcttve acttons-at the hi h 0 rne of th . . g er level e

changes at higher levels 1s more complex than making th s. Makin , em at lo g

It is difficult to change a company s culture, philosophy \Ver levels: . . . . ' or style 'Thi

not mean that you should av01d mvesttgattng high-level causal · s does bili. . . b factors level of accounta ty 1s important- ut everyone should be a --each

only corrective action that is effective is one that is initiated a ware that the by the appropriate decision-makers. nd supported

Hazards vs. Failures

As you investigate accidents, it is important to distinguish between hazards and failures. A hazard is something that has the potential to cause injury, and hazards are correctable. Examples of hazards are a sharp table edge or a pool of grease on the floor.

A failure is something that goes wrong with personnel, equipment, or the environment (Ferry 1981). A failure may or may not have the potential to cause injury. If it does, it is also considered a hazard. A dead battery in an automobile is an example of a failure that is not a hazard; ordinarily it would not cause an accident. However, an automobile tire that fails and blows out while someone is driving is considered a hazard as well as a failure, because the failure could cause an accident.

d fi . d te maintenance, Failures are usually caused by faulty design, a e ect, ma equa limits that were exceeded, or environmental effects.

Analytical Techniques safety . d from systeW

Many accident investigation techniques were derive . f •iures and · t design al techniques that were developed to analyze equipmen f Defense h D artment o hazards. These types of techniques are used by t e ep

and Department of Energy (Vincoli 1994).

d

Chapter 6: The A11a!Jtical Process

There are five main accident investigation techniques. They are introduced here and will be examined in depth in the next part of this book:

, events and causal factors analysis

, change analysis

, barrier analysis

, analytical trees

, cause and effect analysis

Each technique analyzes a different type of problem, and each has strengths and weaknesses. The techniques are broad enough in scope to handle small incidents as well as major catastrophes. Using several techniques in an investigation ensures accuracy, consistency, and validity and helps investigators to obtain more information about the accident sequence, be more accurate and precise, and share investigative responsibilities with others. It is also possible for the results of different techniques to validate each other. These techniques must not be used mechanically or without consideration of the accident sequence and circumstances (DOE 1999).

A flowchart of analytical techniques is illustrated in Exhibit 6.2.

Benefits of Using Analytical Techniques

• If you do not use analytical techniques, it is very easy to find only lower- level causal factors and miss the systemic factors.

• Using analytical techniques for every accident investigation lends consistency to your safety program.

• Analytical techniques will help you to make a smooth and consistent transition from facts to causal factors.

• The thoroughness of the analytical techniques will give you confidence that your investigation determined what really happened and that your recommendations will prevent future accidents.

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Pt111 II: Ort,t1//izf"g tbe [// vestigt1tio//

Exhibit 6.2

Has there been a change in the process?

Is the task recurring? Has it been done accident-free?

Change Analysis

Is there a need to evaluate the loss control efforts or

emergency response1

Time Loss Analysis

Is there a failure of a system or hardware? Could a systematic. evaluation of failure

modes be useful?

Type of Accident

Is there an accident sequence?

Events and Causal Factors Analysis

Has there been a failure of an

engineered or administrative barrier?

Barrier Analysis

Is there an event sequence (event,

problem, or accident)?

Cause and Effect Analysis

Specialized Analytical Techniques

Did a human/machine/ environment interface

or interaction affect the accident?

Human Factors Analysis

Has there been a deviation from the

requirements? Can a review of the codes requirements, and'

standards be useful?

;-r-~~~

. ~."'@~ .. ~ .

Has there been a failure of a system?

Can a deductive approach be useful?

Analytical Trees

Is there a need for a time-based matrix of all personnel at the

accident scene?

Integrated Acc!dent Event Matrix

Is there still a void in the information? can a

specific tes~ or . 7 technique fill thlS void,

"'

Failure Modes and Effects Analysis

------------------------~ Adapted from osHA ins Design Criteria

Analysis

64

Chapter 6: T he A na/ytica/ Process

Summary

The events or circumstances that contribute to an accident are called causal factors. Correction of these causal factors at whatever level they may occur is what ensures that a particular incident will not recur. When using analytical techniques, investigators must be able to distinguish between hazards and failures . Using causal analysis and analytical techniques will make the investigation more effective.

b

REVIEW QUESTIONS 1. What is a causal factor?

2. Describe the four levels of accountability.

3. What is the d ifference between a hazard and a failure?

4. Why is it advisa ble to use more than one an a lytica l technique to investigate an accident ?

65

Part III

ANALYTICAL TECHNIQUES

Pm III focuses on how to analyze an accident and detennine what happened. It explains events and causal factors analysis, change analysis, barrier analysis, analytical trees, and cause and effect analysis as well as some other accident investigation tools and techniques.

Part III also introduces a fictional accident scenario that will be used to demonstrate techniques throughout the rest of the book, with each demonstration building on the ones before it. The scenario is not intended to fully analyze an accident but simply to demonstrate accident investigation techniques.

I,yury:

When:

Where:

ACCIDENT SCENARIO

Employee fell off a ladder and suffered a broken arm and a concussion.

7:45 A.M., February 5, 2011

Warehouse

Accident Description: Bill, a recently hired warehouse supervisor, was hanging up a new exit sign to comply with NFP A Life Safety Code requirements. During a recent warehouse expansion, new rows had been added, and the fire inspector, during his visit the

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Purl /[[: A 11ab'tical Tech11iqJ1eS

68

. d had noted that new exit signs needed to be install d previous ay, . . . e .

ill d to correct the violation as soon as possible

B wante · He arrived at work before his shift beg~-while the night shift was still stocking shelves-to hang the signs. He placed a ladder at the end of an aisle between two rows and climbed the ladder to hang the sign. A forklift driver coming down the next aisle turned the corner and hit the ladder. Bill fell and landed on his arm and head. The forklift driver was not injured. She immediately alerted her supervisor and the proper medical personnel were called.

Other Jnjo17!1ation: This was a non-recurring task. There were no written job procedures for this exact task; however there were procedures for changing light bulbs, a similar task. There were also procedures for working on ladders and procedures for work- ing in the aisles of the warehouse. There was no discussion or review of potential hazards associated with this task. Bill's shift started at 8:00 A.M. Night shift personnel were taking their last load to the warehouse before taking the forklifts to the recharging area. Communication between the shifts and within management had always been a problem. Bill was new to supervision; he had just completed supervisor training the week before. The forklift

driver was properly trained.

Objectives for Part III:

• Understand the analytical techniques used for accident investigations.

• Be able to perform an events and causal factors analysis, change analysis, barrier anal · al · · c accident. ysis, an yttcal tree, and cause and effect analysis 1or any

• Have a ge al kin d puterized ner wor g knowledge of other specialized an com techniques.