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Introduction to Accidents(Module 1)

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Definitions of an Accident

An accident is an unintended, unplanned single or multiple event sequence that is caused by unsafe acts, unsafe conditions or both and may result in immediate or delayed undesirable effects.

(Brauer 1994)

因不安全行為與不安全狀況單獨或協同作用所造成之單次或多次無意、未經策劃的一連串事件，而導致立即或延遲發生的不樂影響。

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To the safety specialist, every accident has one or more identifiable causes. Chance may play a role in bringing causes together.

There are two fundamental types of accident causes: a. unsafe acts b. unsafe condition

Accident involve either of these two causes or both. Recognizing that accidents are caused and not just functions of chance allows one to pursue accident prevention. Some safety specialist replace the term of “accident” to “incidence”.

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Accidents tend to have a range of potential adverse consequences:

Likely Consequences Example

1. A hazardous An operator activates a tagged situation out piece of equipment. The technician working on the equipment is at lunch.

2. Near miss An employee slips in an oil spill but recovers her balance.

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Likely Consequences Example

3. Property The tines of a forklift pierce a damage carton, destroying the product within it.

4. Minor injury Carpenter hit his thumb with a hammer.

5. Serious injury Employee's arm is caught by conveyor belt, dragging the arm to a roller and breaking his arm.

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Most accidents do not include injury or significant loss.Heinrich's Injury Pyramid

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Heinrich's Injury Pyramid

The variation in accident consequences was recognized early this century by Heinrich (1931) with his injury pyramid.

These figures relate to a group of 330 similar accidents. They demonstrate the degree of variation involved with one type of hazard. They should not be considered to be definitive. Other authors, such as Heinrich, Petersen and Roos (1980) and Hoyos and Zimolong (1988), quote different ratios.

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Inverted Reporting Pyramid

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Inverted Reporting Pyramid

We are rarely able to measure the number of accidents that actually occur. We measure the number of accidents that are reported.

In general, the less severe the resultant injury, the less likely it will be reported.

Alongside Heinrich's "injury pyramid" there therefore exists an inverted "reporting pyramid". For every near miss that is reported, there are hundreds to thousands of lost time injuries that are reported.

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Type of loses

Losses from accidents can take many forms, including:

Human: loss of time, medical services, hospitalization, rehabilitation.

Materials(物 ): damage to property, equipment and materials(物料 ).

Others: travel, record keeping, investigation, clean-up, legal services, loss of production and sales, loss of public image.

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Severity of Consequences (loss)

The severity of the consequences will depend upon factors such as:

1. the nature of the hazard;2. the quantity of hazard involved (eg. airborne concentration of solvent, kinetic energy of flying object); 3. the duration of contact or exposure; 4. part of body affected; and 5. important factors unrelated to the hazard itself, eg, luck and individual factors.

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Direct versus indirect costs

Direct costs typically include medical expenses and compensation paid to an injured employee for time away from work and costs for repair or replacement of damaged items.

Indirect costs are real expenses associated with accidents, but difficult to assess for an individual case.

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Based on his own investigation in 1926, Heinrich introduced the “4 : 1 ratio,” which suggests that the total cost associated with accidents is much higher than the obvious, direct expenses.

Although the ratio varies for different companies and different types of operations, the basic idea is sound.

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Unsafe acts and unsafe conditions

Heinrich analyzed 75,000 accidents and found that 88% were caused by unsafe acts, 10% from unsafe conditions and 2% from unpreventable causes. This is Heinrich’s 88:10:2 ratio.

Engineers not only have many opportunities to eliminate or reduce unsafe conditions, but also have many opportunities to minimize unsafe acts. Design that reflect and understanding of human error and behavior can limit the range of human behavior that leads to or causes accidents.

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Accident - cost relationships

Gordon Lembke recognizes that costs are unequally distributed for similar accidents.

For a group of similar accidents resulting in injuries and direct costs (insurance claims), onlya small percentage of the injuries account for most of the total costs of the group and a majority of the injuries account for merely a small portion of the total injury cost.

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Theories of Accident Causes

1. Domino Theory (骨牌理論）

2. Energy Theory（能量理論）

3. Single Factor Theory (單因子理論）

4. Multiple Factor Theory （多因子理論）

5. Psychological/Behavioral Accident Causation Theories (心理 /行為理論）

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Domino Theories

There are three different domino theories of accident causation:

Heinrich’s

Bird and Loftus’, and

Marcum’s Domino Theories.

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Each domino theory presents a different explanation for the cause of accidents, however, each theory is predicated on the fact that there are three phases to any accident.

The three phases are the pre-contactphase, the contact phase and the post contact phase.

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The pre-contact phase are the events or conditions that lead up to the accident.The contact phase is the phase when the accident actually occurs.The post-contact phase refers to the results of the accident.

Domino theories represent accidents as causal factors or hazard events. Each causal factor affects the others if allowed to build up overtime (pre-contact phase). Without intervention, the hazards will interact to cause the accident and move into the contact phase. Thus thederivation of the theory’s name as Domino.

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Heinrich’s Domino Theory

Heinrich’s domino theory essentially states that there are five series factors that could influence an accident. The factors occur sequentially and consist of the following:

1. A negative trait or factor is present in a person as a result of social influence of environment

2. The negative trait or factor may lead to an unsafe practice or condition

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3. The unsafe practice results in an unsafe condition, or it results in mechanical or physical hazards that are the direct cause of an accident

4. Accidents that result from the above process are typically the result of falls or impacts with other moving objects

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5. Injuries from above are usually of the form of lacerations and fractures. As a result of this process, intervention or elimination of any of the first four factors will stop the injury or loss.

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Bird and Loftus’ Domino Theory

series factors that could influence an accident. However, this theory states that the ultimate responsibility for the welfare of the employees Lie with the management of an organization. It is the manager of the organization who can instill the controls necessary to prevent theinitiation of the domino effect.

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1. Lack of Control – Management

Control in this instance refers to the four functions of a manager:

planning, organizing, leading and controlling. Examples of this domino are purchasing substandard equipment or tools, not providing adequate training, or failing to install adequate Engineering controls.

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2. Basic Cause(s) - Origin(s)

The basic causes are frequently classified into a personal factors group and a job factors group. Personal factors may be lack of knowledge or skill, improper motivation, and physical or Mental problems; job factors include inadequate work standards, inadequate design or maintenance, abnormal tool or equipment wear and tear, and abnormal tool usage.

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3. Immediate Cause(s) - Symptoms.

The primary symptoms of all incidents are unsafe acts and unsafe conditions.

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4. Incident – Contact

An undesired event occurs. The accidents are often represented by the eleven accident types,Including:

stuck-by, caught-in, fall-to-belowstruck-against, caught-on, overexertioncontact-by, caught-between, exposurecontact-with, foot-level-fall(source: ANSI Z 16.2)

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5. People – Property – Loss

Result of the accident. The effects are property or environment damage or injury to personnel.

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Marcum’s Domino Theory

According to C. E. Marcum’s 1978 Seven Domino Sequence of Misactsidents, a misactsident is an identifiable sequence of misacts associated with inadequate task preparation which could lead tosubstandard performance and miscompensated risks.

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Marcum also includes the cost aspect of a loss. Like the previous theory, Marcum states that management is ultimately responsible to ensure that the workplace is designed with adequate controls to protect employee.

His seven domino sequences are:

Inadequate preparationSubstandard performanceMis-compensated risk(s)Harmful contact incident

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Adverse reactionSustained lossesIncurred costs

Through this domino theory, Marcum shows that accidents can be prevented by the management by properly training the employees as well as designing adequate controls into the work process.

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The Three Stages of Lost Control

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Pre-Contact Stage:

At this stage, management should be concerned with issues such as engineering practices in the design of new or modified facilities, purchasing practices in the procurement of new materials and equipment, and the development of work standards that could have loss potential implications.

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The supervisor’s application of personal motivation practices, job indoctrination, standard job procedures, proper instruction,and the use and enforcement of rules in the work areas are elements in the pre-contact stage that may actually prevent the first domino from falling.

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Contact stage

It is important that management require the reporting of all non-loss incidents or “near misses” in order to implement appropriate corrective action before repetitive incidents occur that could have loss results.

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Post -Contact Stage

Emergency response

The availability and immediate provision of emergency care has proven time and again to be an effective measure to reduce the frequency of death and disability.

Personnel should be trained and ready to cope with all types of potential emergencies that could arise in their work environments.

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Rehabilitation

Injured workers can remain off the job for quite extended periods of time.

A management policy that focuses on rehabilitation of the injured worker into other jobs or tasks will retain the employee’s intrinsic value to the organization while reducing the overall loss resulting from an accident.

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Prompt repair actions

There are many occasions where prompt maintenance and repair of equipment can reduce the potential for greater loss or damage to property. Management should be alert for any evidence of property damage or premature wear-out of equipment. Small cracks in machines, equipment, or building structures can frequently be repaired easily in the early stages of their development.

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Energy Theory (能量理論）

William Haddon (1970) proposed the idea that many accidents and injuries involve the transfer of energy.

The energy theory suggests that quantities of energy, means of energy transfer and rates of transfer are related to the kind and severity of injuries.

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Later, in 1972, Haddon proposed a matrix (called Haddon’ matrix) to combine factors and phases involved in the injury process.

Factors

Phases Human Vehicle Environment

Pre-event 1 5 9

Event 2 6 10

Post-event 3 7 11

Results 4 8 12

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For example in a motor vehicle crash:

Phase Human Vehicle Environment

Pre-event sleepy, tired, good engine, snowy road, alcohol- lights on, down-hill, dark intoxicated

Event not wearing air-bag tree, utility poles seat belt, side-beam bridge abutments, tissue tolerance of crash force

Post-event bleeding, damage EMT fracture

Results injury, $ repairs, $ social costs

Safety 80

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Using energy transfer as the accident-injury model, Haddon suggests 10 strategies for preventing or reducing losses.

1. Prevent the marshalling of energy. (prevent the creation of the hazard in the first place)

In this strategy the goal is not producing energy or changing it to a form that cannot cause an accident or injury.

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Examples: not producing gun power, substituting a safe substance for a dangerous one, preventing the accumulation of snow where avalanches are possible, not letting small children climb to levels above the floor and not letting a vehicle in motion.

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2. Reduce the amount of energy marshalled. (reduce the amount of the hazard brought into being)

Examples: keeping vehicle speeds down, reducing the quantities or concentration of high energy or toxic materials, limiting the height to which objects are raised and reducing machine speed to the minimum needed when a machine is unguarded for cleaning or maintenance.

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3. Prevent the release of energy. (prevent the release of the hazard that already exists)

Examples: using various means or devices to prevent elevators from falling, flammables from igniting or foundations from being undercut by erosion.

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4. Modify the rate at which energy is released from its source or modify the spatial distribution of the released energy.

Examples: reducing the slop of the road, limit the weight of luggages in the airport

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5. Separate in space or time the energy being released from the structure that can be damaged or the human who can be injured.

Examples: separate paths for vehicular and pedestrian traffic, placing electric power out of reach, using traffic signals to phase pedestrian and vehicular traffic.

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6. Separate the energy being released from a structure or person that can suffer loss by interposing a barrier.

Examples: Safety glasses, barrier guards, radiation filters or shields, median barriers on roadways, thermal insulation and explosive barricades.

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7. Modify the surface of structures that come into contact with people or other structures.

Examples: Rounded corners, blunt objects, dull edges and larger surface areas for tool handles.

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8. Strengthen the structure or person susceptible to damage. (Make what is to be protected more resistant to damage from the hazard)

Examples: fire and earthquake-resistant construction of buildings, training of personnel and vaccination for diseases.

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9. Detect damage quickly and counter its continuation or extension. Examples: Sprinklers that detect heat and spray water to prevent the spread of a fire.

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10. During the period following damage and the return to normal conditions, take measures to restore a stable condition.

Examples: rehabilitating an injured worker and repairing a damaged vehicle.

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Energy Release Theory

According to this theory, an accident is caused by a lack of engineering control. This lack of control results in energy that is out of control which puts causes stress limits to be violated, whether on a person, machinery, or environment. Therefore, accidents can be prevented byinstilling a proper engineering control to divert the energy, which is the source of the hazards.

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Single Factor Theory

This theory is very limited in that it assumes that every accident has only a single and simple cause.

An application of this theory can be demonstrated by reviewing what causes a forklift operator puncturing a radioactive storage drum.

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According to this theory, the cause of theaccident is the forklift.

Yet, by identifying this cause would not mitigate or stop the problem. This theory fails to look at other contributing factors such as workers’ training, storage method, or corrective actions.

This myopic focus makes this theory useless for accident and loss prevention.

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Multiple Factors Theory

The multiple factors theories use four M factors, as shown below:

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Multiple factors theories attempt to identify the hazardous condition (pre-contact) that exist in an operation by revealing the causes that will lead to an accident.

Machine: tools, equipment, or vehicles that may contribute to an accidents; usually characterized by design, shape, size, specific type of energy used to operate equipments

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Media: environmental conditions surrounding an accident, such as weather, walking surface; usually characterized by gender, age, height, weight, condition, memory, recall, knowledge level

Man: people and human factors that could contribute to an accident; usually characterized by snow or water on a roadway, temperature of a building,

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Management: method used to select equipment, train personnel, or ensure a relatively hazard-free environment; usually characterized by safety rules, organization structure, policy and procedures

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Multiple Factor Theories 2

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Multiple Factor Theories 3

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Multiple Factor Theories 4

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Multiple Factor Theories 5

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Multiple Factor Theories 6

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Systems Theory of Causation

This theory states that the probability of an accident lies with how the worker, machine, and environment interact with each other.

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For example the knowledge, skills, and ability, whether acquired through training or gained from years of experience, influences the way a person deciphers the information regarding the environment as well as how he will use the machinery.

This, in effect, will affect his decision makingand therefore will have a bearing on the person performing a job and therefore influence the probability of a mishap.

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Psychological/Behavioral Accident Causation Theories

1. Goals Freedom Alertness TheoryAccording to this theory, accidents are the result of low-quality worker behavior. Correction to this behavior is in the form of raising workerawareness through a positive organizational culture and psychological climate. For example, ensuring that workers are disciplined to maintain good housekeeping will reduce mishaps.

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2. Motivation Reward Satisfaction ModelThis theory builds upon the previous theory. According to this theory, rewards are the factor that have the greatest effect upon performance.If rewards are fairly disseminated as perceived by the employees, there is an increased likelihood of motivation which will produce positive safety results.

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For example, one of the DOE sites decided to implement a program where a pool of safety fund is allotted at the beginning of the year. For every accident, a certain amount of money is reduced from the original allocation. Then at the end of the year, the remaining funds, if any are divided up among the employees. Since starting this program, the number of mishaps have decreased significantly.

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Human Factors Theory

This theory is based on the fact that human errors cause accidents. The three human factors which can lead to human errors areoverload, inappropriate activities, and inappropriate response.

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Overload can occur when a person must perform excessive number of tasks. Despite whether this person is qualified or not, it is theoverburden situation which creates the scenario for a mishap.

An inappropriate activity can occur when a person is not adequately trained to perform his duties. This is one of the reasons for ensuringthat any trainee performing a “real” task during an on-the-job training is supervised at all times.

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An inappropriate response occurs when a qualified person purposely violates a procedure for productivity or he fails to correct the problem when it is detected.