theory of accident

Theory of AccidentTheory of Accident

What is Accident?What is Accident?

An accident can be defined as an An accident can be defined as an unplanned event or happening. unplanned event or happening.

That is, an accident is something That is, an accident is something unexpected, not predictable, foreseen or unexpected, not predictable, foreseen or intended. intended.

What is Accident?What is Accident?

An extension of this theme is that an An extension of this theme is that an accident is an outcome of an event that is accident is an outcome of an event that is not desired. Accidents do not just not desired. Accidents do not just "happen" they are caused. An unsafe act "happen" they are caused. An unsafe act and / or unsafe condition cause the and / or unsafe condition cause the accident event; resulting in interruption to accident event; resulting in interruption to work activities, damage to property or work activities, damage to property or injury to a person. injury to a person.

Accident PyramidAccident Pyramid

1 Major injury

29 Minor injuries

300 Near misses

330 Cases

Hidden Costs Of AccidentsHidden Costs Of Accidents

DIRECT COSTSDIRECT COSTS Medical costsMedical costs Indemnity Indemnity

payments payments (compensation/ (compensation/ insurance)insurance)

INDIRECT COSTSINDIRECT COSTS Lost time by: injured, Lost time by: injured,

onlookers, supervisor, onlookers, supervisor, admin staffadmin staff

Cost of hiring and Cost of hiring and training new employeetraining new employee

Lost profitsLost profits Decreased moraleDecreased morale

Hidden Costs Of AccidentHidden Costs Of Accident

Medical

Indemnity

Lost Time

Lost Profits

Overtime

DIRECT

INDIRECT

National and international National and international authorities, interest authorities, interest

groups, and the publicgroups, and the public

Industry, workers, local authorities, and individuals

Iceberg’s LossIceberg’s Loss

Major Loss Small

property losses

Occupational injuries and illnesses

Brief interruptions

in commerce

Near

missesA

MajorLoss?

Management system

weaknesses

Random external

event

Isolated human errorsIsolated equipment

failures

1. The Domino Theory1. The Domino Theory

According to W.H. Heinrich (1931), who developed the so-According to W.H. Heinrich (1931), who developed the so-called domino theory, 88% of all accidents are caused by called domino theory, 88% of all accidents are caused by unsafe acts of people, 10% by unsafe conditions and 2% by unsafe acts of people, 10% by unsafe conditions and 2% by “acts of God”. “acts of God”.

He proposed a “five-factor accident sequence” in which each He proposed a “five-factor accident sequence” in which each factor would actuate the next step in the manner of toppling factor would actuate the next step in the manner of toppling dominoes lined up in a row. dominoes lined up in a row.

The sequence of accident factors is as follows:The sequence of accident factors is as follows:• ancestry and social environmentancestry and social environment• worker faultworker fault• unsafe act together with mechanical and physical hazard unsafe act together with mechanical and physical hazard

(condition) (condition) • accidentaccident• damage or injury.damage or injury.


INJURY -INJURY - caused by accidents.caused by accidents. ACCIDENTS -ACCIDENTS - caused by an unsafe act, caused by an unsafe act,

injured person, or an unsafe condition / injured person, or an unsafe condition / work place.work place.

UNSAFE ACTS/CONDITIONS - UNSAFE ACTS/CONDITIONS - caused by caused by careless persons careless persons oror poorly designed or poorly designed or improperly maintained equipment.improperly maintained equipment.

FAULT OF PERSONSFAULT OF PERSONS -- created by social created by social environment or acquired by ancestry.environment or acquired by ancestry.

SOCIAL ENVIRONMENT/ANCESTRY -SOCIAL ENVIRONMENT/ANCESTRY - where where and how a person was raised and educated.and how a person was raised and educated.

Social Environmentand Ancestry

Fault of the Person

(Carelessness)

Unsafe Act or

ConditionAccident Injury

MISTAKES OF PEOPLE


In the same way that the removal of a single In the same way that the removal of a single domino in the row would interrupt the domino in the row would interrupt the sequence of toppling, Heinrich suggested sequence of toppling, Heinrich suggested that removal of one of the factors would that removal of one of the factors would prevent the accident and resultant injury; prevent the accident and resultant injury; with the key domino to be removed from with the key domino to be removed from the sequence being number 3.the sequence being number 3.

Although Heinrich provided no data for his Although Heinrich provided no data for his theory, it nonetheless represents a useful theory, it nonetheless represents a useful point to start discussion and a foundation point to start discussion and a foundation for future research.for future research.


2. Multiple causation theory2. Multiple causation theory

Multiple causation theory is an outgrowth Multiple causation theory is an outgrowth of the domino theory, but it postulates of the domino theory, but it postulates

that for a single accident there that for a single accident there

may be many contributory may be many contributory

factors, causes and factors, causes and

sub-causes, and sub-causes, and

that certain combinations that certain combinations

of these give rise to accidents. of these give rise to accidents.

According to this theory, the contributory According to this theory, the contributory factors can be grouped into the following factors can be grouped into the following two categories:two categories:• BehavioralBehavioral. This category includes factors . This category includes factors

pertaining to the worker, such as improper pertaining to the worker, such as improper attitude, lack of knowledge, lack of skills and attitude, lack of knowledge, lack of skills and inadequate physical and mental condition.inadequate physical and mental condition.

• EnvironmentalEnvironmental. This category includes . This category includes improper guarding of other hazardous work improper guarding of other hazardous work elements and degradation of equipment elements and degradation of equipment through use and unsafe procedures.through use and unsafe procedures.

The major contribution of this theory is to The major contribution of this theory is to bring out the fact that rarely, if ever, is an bring out the fact that rarely, if ever, is an accident the result of a single cause or act.accident the result of a single cause or act.

2. Multiple causation theory2. Multiple causation theory

3. Accident-Proneness Theory3. Accident-Proneness Theory

““Injuries happen to people who have a Injuries happen to people who have a genetic predisposition to being injured”genetic predisposition to being injured”

The theory states that there are inherent The theory states that there are inherent characteristics of some individuals that characteristics of some individuals that predispose them to a greater probability of being predispose them to a greater probability of being involved in involved in accidentsaccidents..

Old View


A very controversial theoryA very controversial theory Many research studies have been Many research studies have been

conducted which lend support for the conducted which lend support for the theory (Studies show injuries are not theory (Studies show injuries are not randomly distributed, randomly distributed, butbut do studies do studies recognize differences in hazard recognize differences in hazard exposure?)exposure?)

Other studies have shown that there Other studies have shown that there is no basis for the is no basis for the theorytheory


Recent researchers view accident Recent researchers view accident proneness as being associated with proneness as being associated with the the propensity of individuals to take propensity of individuals to take risksrisks or to take chances. or to take chances.

This presents a more positive view This presents a more positive view for safety, as for safety, as behavior can be behavior can be alteredaltered even if the propensity to even if the propensity to take risks cannot.take risks cannot.

New View

4. The Pure Chance Theory4. The Pure Chance Theory

According to the pure chance theory, According to the pure chance theory, every one of any given set of workers has every one of any given set of workers has an equal chance of being involved in an an equal chance of being involved in an accident. accident.

It further implies that there is no single It further implies that there is no single discernible pattern of events that leads to discernible pattern of events that leads to an accident. an accident.

In this theory, all accidents are treated as In this theory, all accidents are treated as corresponding to Heinrich’s acts of God, corresponding to Heinrich’s acts of God, and it is held that there exist no and it is held that there exist no interventions to prevent them.interventions to prevent them.

5. Biased liability theory5. Biased liability theory

Biased liability theory is based on the view Biased liability theory is based on the view that once a worker is involved in an that once a worker is involved in an accident, the chances of the same worker accident, the chances of the same worker becoming involved in future accidents are becoming involved in future accidents are either increased or decreased as either increased or decreased as compared to the rest of workers.compared to the rest of workers.

This theory contributes very little, if This theory contributes very little, if anything at all, towards developing anything at all, towards developing preventive actions for avoiding accidents.preventive actions for avoiding accidents.

6. The energy transfer theory6. The energy transfer theory

Developed by Dr. William Haddon, Jr., of the Developed by Dr. William Haddon, Jr., of the Insurance Institute for Highway Safety. Insurance Institute for Highway Safety.

Those who accept the energy transfer theory put Those who accept the energy transfer theory put forward the claim that a worker incurs injury or forward the claim that a worker incurs injury or equipment suffers damage through a change of equipment suffers damage through a change of energy, and that for every change of energy energy, and that for every change of energy there is a source, a path and a receiver. there is a source, a path and a receiver.

This theory is useful for determining injury This theory is useful for determining injury causation and evaluating energy hazards and causation and evaluating energy hazards and control methodology. control methodology.

Strategies can be developed which are either Strategies can be developed which are either preventive, limiting or ameliorating with respect preventive, limiting or ameliorating with respect to the energy transfer.to the energy transfer.

Control of energy transfer at the source can be Control of energy transfer at the source can be achieved by the following means:achieved by the following means:• elimination of the sourceelimination of the source• changes made to the design or specification of elements changes made to the design or specification of elements

of the work stationof the work station• preventive maintenance.preventive maintenance.

The path of energy transfer can be modified by:The path of energy transfer can be modified by:• enclosure of the pathenclosure of the path• installation of barriersinstallation of barriers• installation of absorbersinstallation of absorbers• positioning of isolators.positioning of isolators.

The receiver of energy transfer can be assisted The receiver of energy transfer can be assisted by adopting the following measures:by adopting the following measures:• limitation of exposurelimitation of exposure• use of personal protective equipment.use of personal protective equipment.

6. The energy transfer theory6. The energy transfer theory

7. The “symptoms versus causes” theory7. The “symptoms versus causes” theory

The “symptoms versus causes” theory is not The “symptoms versus causes” theory is not so much a theory as an admonition to be so much a theory as an admonition to be heeded if accident causation is to be heeded if accident causation is to be understood. understood.

Usually, when investigating accidents, we Usually, when investigating accidents, we tend to fasten upon the obvious causes of the tend to fasten upon the obvious causes of the accident to the neglect of the root causes.accident to the neglect of the root causes.

Unsafe acts and unsafe conditions are the Unsafe acts and unsafe conditions are the symptoms-the proximate causes-and not the symptoms-the proximate causes-and not the root causes of the accident. root causes of the accident.

This theory states that accidents are This theory states that accidents are caused when workers are distracted when caused when workers are distracted when they are performing their work tasks.they are performing their work tasks.

There are two types of distractions.There are two types of distractions.

8. The Distraction Theory

Jobsite Hazards can be a source of Jobsite Hazards can be a source of distractiondistraction• Workers will try to avoid being injured so Workers will try to avoid being injured so

they naturally focus on the hazard, but this they naturally focus on the hazard, but this occurs as they are trying to do work. Trying occurs as they are trying to do work. Trying to get the task done may cause the worker to get the task done may cause the worker to be distracted and to ignore the hazard, to be distracted and to ignore the hazard, resulting in an injury.resulting in an injury.

The Dilemma:

Focus on the Hazards

Focus on Getting Tasks Done

or


low

high

highlow

Work Task Achievement

Distraction: Working near a powerline

low focus on distraction

high focus on distraction

Probability of Injury Occurrence

Safe Zone

low

high

highlow

Work Task Achievement

Distraction: Minor Hazard




Task AchievementLow High

Injury

Occurrence

Low Focus on Hazard

High Focus on Hazard

Task AchievementLow High

Injury

Occurrence

Low Focus on Hazard

High Focus on Hazard

Don’t work in this zone!!!

Mental worries can be a source of Mental worries can be a source of distraction.distraction.• Workers will try to focus on the work to be Workers will try to focus on the work to be

done, but may be distracted by worries caused done, but may be distracted by worries caused by personal or job-related concerns. Failure to by personal or job-related concerns. Failure to be able to focus on the work increases the be able to focus on the work increases the likelihood of being injured.likelihood of being injured.


low

high

highlow Work Task Achievement

Major Mental Distraction




Can distracted workers be identified?

Structure of AccidentsStructure of Accidents

The belief that accidents are caused and The belief that accidents are caused and can be prevented makes it imperative can be prevented makes it imperative for us to study those factors which are for us to study those factors which are likely to favor the occurrence of likely to favor the occurrence of accidents. accidents.

By studying such factors, the root By studying such factors, the root causes of accidents can be isolated and causes of accidents can be isolated and necessary steps can be taken to prevent necessary steps can be taken to prevent the recurrence of the accidents. the recurrence of the accidents.

Structure of AccidentsStructure of Accidents These root causes of accidents can be These root causes of accidents can be

grouped as “immediate” and “contributing”. grouped as “immediate” and “contributing”. The immediate causes are unsafe acts of The immediate causes are unsafe acts of

the worker and unsafe working conditions. the worker and unsafe working conditions. The contributing causes could be The contributing causes could be

management-related factors, the management-related factors, the environment and the physical and mental environment and the physical and mental condition of the worker. condition of the worker.

A combination of causes must converge in A combination of causes must converge in order to result in an accident.order to result in an accident.

Structure of AccidentsStructure of Accidents

Thank YouThank You

theory of accident

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