Acciones jurídicas para el transporte público, 1993-

Thorough identification of the potential hazards can require the use of several different analysis methods. Hazards can be related to the technical system or production process, or to the human acts and behavior. Hazards can also be categorized according to their potential effects. The personnel can be in danger, the surrounding population can be affected, the property can be damaged or the environment can be harmed. In the following, the different types of hazard identification techniques are summarized.

WORKPLACE CHECKLISTS

Checklists are easy-to-use methods for identifying accident hazards related to the physical environment or to the human behavior. Some checklists are very general, while some are developed for a very specific type of environment. An example of a general purpose industrial checklist is the “Major Hazard and OSHA Checklist” presented by Heinrich et al. (1980). Checklists are typically used during a walk-through in the workplace. Some checklists include an option

to calculate a safety index which describes how many elements of the checklist are in order and how many require improvement.

RISK ANALYSIS METHODS

Risk analysis is a systematic examination method, and most commonly used in industrial installations. It aims at identifying the potential accident contributors, evaluating the amount of risk, and finding risk-reducing measures. Risk analysis methods can identify system failures following both from technical defects and human errors. The term “safety analysis” is often used in the same meaning as “risk analysis”. However, there is a tendency to use “risk analysis” merely in the field of major hazards, and the term “safety analysis” in the field of occupational and product safety. (Suokas 1985)

Risk analysis methods used mainly in process industry include HAZOP, FMEA, FTA, and ETA. HAZOP (Hazard and Operability Analysis) is a systematic risk analysis method in which process deviations and potential operating problems are identified using a series of guide words (Lees 1996). FMEA (Failure Mode and Effects Analysis) is based on a tabular form to which the components of the system and their failures and failure modes are listed (IEC 812 1985). FTA (Fault-Tree Analysis) models the sequence leading to the hazard, the so-called TOP-event (Roland & Moriarty 1983). ETA (Event-Tree Analysis) models the potential consequences of failures or events (Wells 1980). Both FTA and ETA can also be used as quantitative methods. Suokas (1985) has studied the reliability and validity related to some of those risk analysis methods.

MORT (Management Oversight and Risk Tree) is a comprehensive tool for managing a company’s safety activities (Johnson 1980). Through the MORT analysis, the adequacy, as well as the realization of the safety activities, can be followed. While the previously described risk analysis methods mainly aim at locating hardware deficiencies and human errors, MORT also assesses the management system.

METHODS TO EVALUATE EXPOSURE TO HUMAN

The stress-strain model presented by Landau & Rohmert (1989) is a practical way to study an individual’s relationship to the work environment (Figure 6). The model can be used for studying an individual’s coping with the different physical, mental, and to some extent the social factors at work.

Figure 6. Simplified stress-strain model (adopted from Landau & Rohmert 1989).

Stress factors are commonly divided into two main categories: 1) physical hazards, and 2) mental (psychological) hazards. This division is useful, but not quite accurate, since these two factors are often linked together. For instance, mental strain can cause physiological symptoms, and physical hazards like high noise level or unsatisfactory thermal conditions can contribute to experienced mental overload. A list of the typical physical hazards and their identification methods is presented in Table 2.

Table 2. The types of physical hazards, and examples of their identification methods.

Physical hazards Typical identification methods

Physical energies Measurement of noise, vibration, illumination, temperature, radiation, and air flow. Health tests, e.g. eyesight and hearing tests.

Muscular work load Analysis of working posture and manual working tasks. Health tests, e.g. fitness tests.

Chemical and biological substances

Evaluation of the harmful effects of chemicals. Industrial hygiene measurements.

The concept of mental stress or (psychological stress) was introduced after the second world war in the field of medicine (Grandjean 1988). Mental stress at work is difficult to measure, because of the great variation in the experienced

Stress factors of the work environment Individual’s skills and abilities STRAIN Work environment

stress between individuals. What is overload to one person can be a balanced situation, a positive experience, or even a challenge to another person.

However, some characteristics of the work environment can be considered as potential sources of harmful mental stress. The quality and quantity of these characteristics can be measured from the work environment itself by using suitable work analysis methods. Examples of these methods are PAQ (Position Analysis Questionnaire) (McCormick et al. 1979), AET (Das Arbeitswissenschaftliche Erhebungsverfahren zur Tätigkeitsanalyse) (Rohmert & Landau 1979), and FSD (Fragebogen zur Sicherheitsdiagnose) (Hoyos 1988). Elo (1994) has developed a checklist that is designed specially for the analysis of mental stressors at work.

An individual’s experienced stress can be measured by questionnaires, interviews, and other methods like physiological measurements. Questionnaires and interviews include methods like JDS (Job Diagnostics Survey) developed by Hackman & Oldham (1975), and OSQ (Occupational Stress Questionnaire) developed by Elo (1994). The correlation between mental strain and physiological symptoms like heart rate, blood pressure and hormone secretion has been known since 1940s (Grandjean 1988).

The social environment comprises of the relationships between people, and it is one potential source of mental stress. Social environment is strongly influenced, e.g. by the organizational culture, the management’s performance, and supervisor’s leadership style. The personnel’s work motivation, commitment, job satisfaction and behavior, among others, reflect the quality of the social environment.