benefit of implementing a risk reduction measure is an estimate of the “cost” reduction implied by fewer injuries and fatalities (expressed through VSL) and also of possibly reduced input resources and/or improved system productivity.
The evaluation of disproportionality is carried out by first defining a disproportionality limit
A challenge with the cost–benefit approach is that it raises the problem of expressing not only the costs but also the risk reduction benefits in monetary terms. This is a particularly sensitive issue when it comes to putting a value on human life as was discussed earlier. To guide decision‐making, some companies use internal criteria for the value of human life. An alternative to such explicit valuation of human life is simply to calculate the cost–benefit ratio for any risk reduction measure and to look out for any clearly unreasonable situations. If the value of life is not quantified, then resources, which also have value, cannot be allocated rationally to develop and implement countermeasures to protect life. For other types of consequences, such as environmental damage, costs also need to be calculated. Clean‐up costs are sometimes used in connection with spills, but these costs do not reflect irreversible damage to species affected by spills.
A particular problem when a comparison of cost and benefit is done in this way is that the costs are deterministic, whereas the benefits are probabilistic. If we decide to implement a risk reduction measure, we know that there will be a cost associated with it. The benefit we gain is a reduction in the probability of an accident occurring or a reduction in the consequences, should an accident occur. Often, the probability of an accident is very low – regardless of whether individual risk measures are introduced or not – such that the accident will not occur even if the risk measure is not introduced. The benefit is thus purely probabilistic.
Another aspect of cost–benefit assessment is the use of discounting of costs and benefits. In financial calculations, this is common to do and implies that future costs and benefits have a lower value than costs and benefits that we get today. In cost–benefit assessment, this is used sometimes, but not always. There are arguments both for and against using this approach, but perhaps the foremost argument can be tied to the occurrence of accidents now versus in the future. If we have a hypothetical situation, where we know that an accident will occur, but we can choose whether it will occur one year from now or 10 years from now, everyone would undoubtedly choose the latter option. In this respect, we can say that future accidents have a lower “cost” than accidents today and that future risk therefore should be discounted.
To summarize, the ALARP principle states that money must be spent to reduce risk until it is reasonably low and must continue to be spent for as long as the cost of doing so is not “grossly disproportionate” and the risk is not negligible. If a “tolerable” level of risk can be reduced further at a reasonable cost and with little effort, it should be. At the same time, the ALARP principle recognizes that not all risk can be eliminated. Because it may not be practicable to take further action to reduce the risk or to identify the accidents that pose the risk, there will always be some residual risk of accidents.
Remark 5.1 (SFAIRP)
In the United Kingdom Health and Safety at Work Act and in other regulations, the term SFAIRP is often used instead of ALARP. The two concepts are similar and can usually be interchanged. SFAIRP is an acronym for “so far as is reasonably practicable.”
5.3.2 The ALARA Principle
ALARA is an acronym for “as low as reasonably achievable,” which is the risk acceptability framework in the Netherlands. The ALARA principle is conceptually similar to ALARP, but does not include any region of broad acceptability. Until 1993, the region of negligible risk was part of the Dutch policy. Subsequently, it has been abandoned on the grounds that all risk should be reduced as long as it is reasonable (Bottelberghs 2000). ALARA has gained a somewhat different interpretation in practice. According to Ale (2005), it is common practice in the Netherlands to focus on complying with the upper limit rather than evaluating the reasonable practicality of further action. The unacceptable region in ALARA is, on the other hand, generally stricter than the one in ALARP, and the risk levels usually end up in the same range.
5.3.3 The GAMAB Principle
GAMAB is an acronym of the French expression globalement au moins aussi bon, which means “globally at least as good.” The principle assumes that an acceptable solution already exists and that any new development should be at least as good as the existing solutions. The expression globalement (in total) is important here because it provides room for trade‐offs. An individual aspect may therefore be worsened if it is overcompensated by an improvement elsewhere.
The GAMAB principle has been used in decision‐making related to transportation systems in France, where new systems are required to offer a total risk level that is globally as low as that of any existing equivalent system. The principle is included in the railway RAMS standard (EN 50126 1999). A recent variant of GAMAB is GAME, which rephrases the requirement to at least equivalent.
GAMAB is a technology‐based criterion, which means that it uses existing technology as the point of reference. By applying this principle, the decision‐maker is exempted from the task of formulating a risk acceptance criterion because it is already given by the present level of risk (e.g. see Johansen 2010).
5.3.4 The MEM Principle
Minimum endogenous mortality (MEM) is a German principle that uses the probability of dying of “technological facts” (e.g. sport, work, transport) as a reference level for risk acceptability. The principle requires that new or modified technological systems must not cause a significant increase of the individual risk for any person (Schäbe 2001). MEM is based on the fact that death rates vary with age and the assumption that a portion of each death rate is caused by technological systems (Nordland 2001).
Endogenous mortality means death due to internal or natural causes. In contrast, exogenous mortality is caused by the external influences of accidents. The endogenous mortality rate is the rate of deaths due to internal causes of a given population at a given time. Children between 5 and 15 have the MEM rate, which in Western countries is about
According to the railway standard (EN 50126 1999), a “significant increase”
