Accident risk: definition

The first step in designing a road safety development index (RSDI) is to come up with a comprehensive set of indicators, which includes as far as possible aU the main parameters in road safely of human-vehicle-road-enviromnent-regulation, instead of considering a few factors such as accident rates per population or per kilometoe driven. In addition, this index should be as relevant as possible for different countries, especially in developing countries. The choice of accident risk and exposure variables is necessary to what is available in international data and what is considered necessary for meaningfiil comparisons. Commonly, frequencies of aimual numbers of vehicles, accidents, injured and killed people are some kind quantification and relatively easy to define and to measure in different countries. But differences in definitions, noncollection of data, non-rehabUity of data and under-reporting are problems for effective measurements of road safety. 

During 1999, the European Commission ARIBA project attempted to build an accident risk tolerability matrix for air traffic operations on UK Health and Safety Executive lines. The main reason for this was due to the fact that UK industry safety assessments usually use the HSE studies and guidelines about tolerable and acceptable risk , with the following (simplified) HSE definitions ... 

The relationships between the importance measures is based on the assumption that the systems are not reconfigured in response to a component outage. If this is done, the basic definition of the importance measure is still valid but there is not such a simple relationship. Disregarding this complication, some interpretations of the importances may be made. The Bimbaum Importance is the risk that results when the i-th system has failed (i.e., it is the A, term in Equation 2.8-9). Inspection Importance and RRWI are the risk due to accident sequences containing the i-th system. Fussell- Vesely Importance is similar except it is divided by the risk so may be interpreted as the fraction of the total risk that is in the sequences contains the Q-th system. The Risk Achievement Worth Ratio (RAWR) is the ratio of the risk with system 1 failed to the total risk and is necessarily greater than one. The Risk Achievement Worth Increment (RAWI) is the incremental risk increase if system 1 fails and the Risk Reduction Worth Ratio (RRWR) is the fraction by which the risk is reduced if system 1 were infallible. 

The process begins with initial system and accident definition for which accidem the probabilities and consequences must be determined to give the risk (Figure 6,3-1). Item 1, (he event tree is central to PSA because it diagrams the accident scenarios to connect accident imtiaiors to consequences. 

Additionally, chronic drug use has been linked to neuropsychological problems that in turn make it harder to stop the cycle of abuse. Psychoactive drugs by definition affect the brain, and long-term or acute exposure to psychoactive substances can be toxic. Furthermore, we know that drug abuse can increase the risks of stroke, brain injury related to accidents, malnutrition, or liver damage, all of which can adversely affect brain function as well. 

Before scientifically sound research can be performed on a subject, clear definitions must be set. Although, this may seem a logical step, Osborn (Osborn et al., 1988) highlighted that this has been a stumbling block for research in safety science since its inception. Definitions of concepts like accidents, incidents, near misses, risk, and safety, are known in the field of safety science, but interpreted differently in various situations. Unclear and ambiguous definitions lead to misinterpretations and confusion and must be avoided. Therefore, some general concepts used in safety science and the definitions used in this thesis are discussed in this Section. In the remainder of this thesis specific concepts will be defined where appropriate and can also be found in a list of acronyms and definitions presented in the beginning of this thesis. 

The definition of risk from Chapter 1 is used to set up an analysis tool to find a possible link between Sis and recent accidents. The following sub-Section will therefore introduce this analysis tool before analysing current safety indicators and accidents. 

Therefore, Chapter 4 will give a detailed definition of these precursors and a way to identify them in practice. Moreover, causes for the occurrence of these precursors will be identified to retrieve a better understanding of why accidents still occur, and this will be closely linked to the normal way of working. From these concepts a model will be developed which can approach practice in a straightforward pro-active way, without the need to possess any expert knowledge and which provides clear directions for improvements in identifying safety related risks. 

Before discussing risk assessment techniques, it is worthwhile to review what produces hazards. A recent definition of an accident by W. G. Johnson, former General Manager of the National Safety Council professional staff and author of MORT Safety Assurance Systems, provides an excellent basis for determining what produces hazards. According to Mr. Johnson, the elements involved in an accident are ... 

Only in a limited number of countries have individual risk limit values courageously been defined. One famous definition is the British Fatal Accident Rate (FAR). Operations with a FAR of less than 0.4 are regarded as safe. The FAR is defined as the number of fatalities per 1000 employees in their average working life time of 25 years. The answer to the question whether those relatives who have just lost a loved one find consolation in the statement that the probability for one worker in a company with 1000 employees to die fi om the consequences of a process is once in 30000 years can easily be found by the reader. 

An initiating event is an event that triggers an accident sequence—e.g., a wave that exceeds the jacket s capacity that, in turn, triggers a blowout that causes failures of the foundation. As initiating events, they are mutually exclusive only one of them starts the accident sequence. A catastrophic platform failure can start by failure of the foundation, failure of the jacket, or failure of the deck. These initiating failures are also (by definition) mutually exclusive and constitute the basic events of the [probabilistic risk assessment] model in its simplest form. [152, p. 121]... 

Another possible explanation of the observed reactions are the additives in pharmaceutical preparations. Thus Lagerholm et al. (1958) reported a case of hypersensitivity to benzyl alcohol added as a preservative to vitamin B 2 preparations, resulting in urticaria after injection, Hovding (1968), however, was not able to demonstrate a positive skin reaction either with benzyl alcohol or with cobalt chloride. However, skin tests with commercial brands of cyanocobalamin and hydroxocobalamin as well as with purified cyanocabalamin and hydroxocobalamin were positive. Malten (1975) reports a flare reaction in a woman due to the third injection of 250 pg vitamin B12. Prick and patch tests, however, remained negative. A recent short review of reactions after administration of vitamin Bj2 preparations was published by Meuwissen (1978). An extensive review covering the literature up to 1975 was presented by Faivre et al. (1975). The authors conclude that, despite the widespread use of vitamin B12 preparations, cases of accidents after vitamin Bi2 administration are very rare, but nevertheless are a potential risk. Therefore, skin and immunologic tests should be made prior to administration and especially parenteral application of the vitamin. The authors do not make an explicit statement as to a definite allergic mechanism of the observed phenomena. 

The definition of an accident contained in the original literature on MORT management oversight and risk tree) indicated that an injury was preceded by sequences of planning and operational errors which (a) failed to... 

This definition of an accident appears in the Guide to Use of the Management Oversight and Risk Tree An accident is defined as unwanted transfer of energy or environmental condition because of lack or inadequate barriers an or controls, producing injury to persons and/or damage... 

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