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As low as reasonably practicable
As low as reasonably practicable (ALARP), or as low as reasonably achievable (ALARA), is a principle in the regulation and management of safety-critical and safety-involved systems. The principle is that the residual risk shall be reduced as far as reasonably practicable. In UK and NZ Health and safety law, it is equivalent to so far as is reasonably practicable (SFAIRP). In the US, ALARA is used in the regulation of radiation risks.
For a risk to be ALARP, it must be possible to demonstrate that the cost involved in reducing the risk further would be disproportionate to the benefit gained.
Determining that a risk has been reduced to ALARP involves an assessment of the risk and costs involved in taking measures to avoid that risk, and a comparison of the two according to cost–benefit analysis (CBA). In this context, risk is the combination of the frequency (likelihood) and the consequence of a specified hazardous event. Several factors are likely to be considered when deciding whether or not a risk has been reduced as far as reasonably practicable:
A difficulty arising in CBAs is assigning a meaningful and agreed financial value of life. In the context of ALARP, financial values to impacts to the environment, physical assets, production stoppage, company reputation, etc. are assigned, which also presents significant challenges to the analysis.
'Carrot diagrams' show high (normally unacceptable) risks at the upper/wider end and low (broadly acceptable) risks at the lower/narrower end, with a 'tolerable' or 'ALARP' region in between. They were originally developed by the Health and Safety Executive (HSE) to illustrate their framework for the Tolerability of Risk (TOR), which set out the HSE's approach to regulating safety risks. While the ALARP principle applies at all levels of risk under UK health and safety law, the TOR framework captures the concept that some risks are too great to be acceptable, whatever the benefit; while others are so low as to be insignificant. The HSE, as regulators, would not usually require further action to reduce these broadly acceptable risks unless reasonably practicable measures were available, although they would still take into account that duty holders must reduce risks wherever it is reasonably practicable to do so. Between the two extremes, risks can be tolerated in order to secure benefits, so long as they have been risk assessed and are kept ALARP.
Carrot diagrams are sometimes known as 'ALARP Triangles'. However, this can be misleading because they illustrate the Tolerability of Risk framework rather than the ALARP principle itself, and can be misinterpreted as meaning either that ALARP legally applies only in the tolerable region, or that risks in tolerable region are automatically ALARP.
The term ALARP arises from UK legislation, particularly the Health and Safety at Work etc. Act 1974, which requires "Provision and maintenance of plant and systems of work that are, so far as is reasonably practicable, safe and without risks to health". The phrase So Far As is Reasonably Practicable (SFARP) in this and similar clauses is interpreted as leading to a requirement that risks must be reduced to a level that is As Low As is Reasonably Practicable (ALARP).
The key question in determining whether a risk is ALARP is the definition of reasonably practicable. This term has been enshrined in the UK case law since the case of Edwards v. National Coal Board in 1949. The ruling was that the risk must be significant in relation to the sacrifice (in terms of money, time or trouble) required to avert it: risks must be averted unless there is a gross disproportion between the costs and benefits of doing so.
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As low as reasonably practicable
As low as reasonably practicable (ALARP), or as low as reasonably achievable (ALARA), is a principle in the regulation and management of safety-critical and safety-involved systems. The principle is that the residual risk shall be reduced as far as reasonably practicable. In UK and NZ Health and safety law, it is equivalent to so far as is reasonably practicable (SFAIRP). In the US, ALARA is used in the regulation of radiation risks.
For a risk to be ALARP, it must be possible to demonstrate that the cost involved in reducing the risk further would be disproportionate to the benefit gained.
Determining that a risk has been reduced to ALARP involves an assessment of the risk and costs involved in taking measures to avoid that risk, and a comparison of the two according to cost–benefit analysis (CBA). In this context, risk is the combination of the frequency (likelihood) and the consequence of a specified hazardous event. Several factors are likely to be considered when deciding whether or not a risk has been reduced as far as reasonably practicable:
A difficulty arising in CBAs is assigning a meaningful and agreed financial value of life. In the context of ALARP, financial values to impacts to the environment, physical assets, production stoppage, company reputation, etc. are assigned, which also presents significant challenges to the analysis.
'Carrot diagrams' show high (normally unacceptable) risks at the upper/wider end and low (broadly acceptable) risks at the lower/narrower end, with a 'tolerable' or 'ALARP' region in between. They were originally developed by the Health and Safety Executive (HSE) to illustrate their framework for the Tolerability of Risk (TOR), which set out the HSE's approach to regulating safety risks. While the ALARP principle applies at all levels of risk under UK health and safety law, the TOR framework captures the concept that some risks are too great to be acceptable, whatever the benefit; while others are so low as to be insignificant. The HSE, as regulators, would not usually require further action to reduce these broadly acceptable risks unless reasonably practicable measures were available, although they would still take into account that duty holders must reduce risks wherever it is reasonably practicable to do so. Between the two extremes, risks can be tolerated in order to secure benefits, so long as they have been risk assessed and are kept ALARP.
Carrot diagrams are sometimes known as 'ALARP Triangles'. However, this can be misleading because they illustrate the Tolerability of Risk framework rather than the ALARP principle itself, and can be misinterpreted as meaning either that ALARP legally applies only in the tolerable region, or that risks in tolerable region are automatically ALARP.
The term ALARP arises from UK legislation, particularly the Health and Safety at Work etc. Act 1974, which requires "Provision and maintenance of plant and systems of work that are, so far as is reasonably practicable, safe and without risks to health". The phrase So Far As is Reasonably Practicable (SFARP) in this and similar clauses is interpreted as leading to a requirement that risks must be reduced to a level that is As Low As is Reasonably Practicable (ALARP).
The key question in determining whether a risk is ALARP is the definition of reasonably practicable. This term has been enshrined in the UK case law since the case of Edwards v. National Coal Board in 1949. The ruling was that the risk must be significant in relation to the sacrifice (in terms of money, time or trouble) required to avert it: risks must be averted unless there is a gross disproportion between the costs and benefits of doing so.