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36 Definitions Acceptable Level of Risk. For regulations and special per- Quantitative Risk Analysis. Incorporates numerical estimates mits, the acceptable levels of risk are established by consider- of frequency or probability and consequence. ation of risk, cost/benefit, and public perception. Risk. The combination of the likelihood and the consequence Accident. An unplanned event or series of events that results of a specified hazard being realized. It is a measure of harm or in death, injury, damage to, or loss of, equipment or property. loss associated with an activity. Consequence. The direct effect of an event, incident, or acci- Risk Analysis. The study of risk in order to understand and dent. In this study, it is expressed as a health effect (e.g., death, quantify risk so it can be managed. injury, exposure) or property loss. Risk Assessment. Determination of risk context and accept- Hazard. The inherent characteristic of a material, condition, ability, often by comparison to similar risks. or activity that has the potential to cause harm to people, property, or the environment. Safety. Freedom from unacceptable risk. Often, safety is equated with meeting a measurable goal, such as an accident Hazard Analysis. The identification of system elements, rate that is less than an acceptable target. However, the absence events, or material properties that lead to harm or loss. The of accidents does not ensure a safe system. To remain vigilant term "hazard analysis" may also include evaluation of conse- regarding safety, it is necessary to recognize that just because quences from an event or incident. an accident has not happened does not mean that it cannot or Incident. A near-miss episode, malfunction, or failure with- will not happen. out accident-level consequences that has a significant chance Safety Risk Management. The systematic application of of resulting in accident-level consequences. policies, practices, and resources to the assessment and con- Likelihood. Expressed as either a frequency or a probability. trol of risk affecting human health and safety and the envi- Frequency is a measure of the rate at which events occur over ronment. Hazard, risk, and cost/benefit analysis are used to time (e.g., events/year, incidents/year, deaths/year). Probabil- support the development of risk reduction options, pro- ity is a measure of the rate of a possible event expressed as a gram objectives, and prioritization of issues and resources. fraction of the total number of events (e.g., 1 in 10 million, A critical role of the safety regulator is to identify activities 1/10,000,000, or 110-7). involving significant risk and to establish an acceptable level of risk. METAR. Aviation routine weather report. Veer-Off. An aircraft running off the side of the runway dur- Nonconformity. Non-fulfillment of a requirement. This in- ing takeoff or landing roll. cludes, but is not limited to, non-compliance with federal reg- ulations. It also includes an organization's requirements, Worst Credible Condition. The most unfavorable condi- policies, and procedures, as well as requirements of safety risk tion or combination of conditions that it is reasonable to controls developed by the organization. expect will occur.