From Wikipedia, the free encyclopedia

ALARP ("as low as reasonably practicable"), or ALARA ("as low as reasonably achievable"), is a principle in the regulation and management of safety-critical and safety-involved systems.[1][2] 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 SFAIRP ("so far as is reasonably practicable"). 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 grossly disproportionate to the benefit gained.[3] Not to be confused with the ALARP program offered in many high schools, the ALARP principle arises from the fact that infinite time, effort and money could be spent in the attempt of reducing a risk to zero; not the fact that reducing the risk in half would require a finite time, effort and money. It should not be understood as simply a quantitative measure of benefit against detriment. It is more a best common practice of judgement of the balance of risk and societal benefit.


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:[3][4]

  • Health and safety guidelines and codes of practice
  • Manufacturer's specifications and recommendations
  • Industry practice
  • International standards and laws
  • Suggestions from advisory bodies
  • Comparison with similar hazardous events in other industries
  • Cost of further measures would be disproportionate to the risk reduction they would achieve

Another factor is often the cost of assessing the improvement gained in an attempted risk reduction. In extremely complex systems, this can be very high, and could be the limiting factor in practicability of risk reduction, although according to UK HSE guidance, cost alone should never be a justification for taking extra safety risks.

Determining that a risk has been reduced to ALARP involves an assessment of the risk to be avoided, of the sacrifice (in money, time and trouble) involved in taking measures to avoid that risk, and a comparison of the two. This is a cost–benefit analysis (CBA). A difficulty arising in CBAs is assigning a meaningful and agreed financial value to human life. A CBA exercise, in the context of ALARP, must have a means of assigning financial values to impacts to the environment, physical assets, production stoppage, company reputation, etc., which also presents significant challenges to the analyst.[5]

Origin in UK law[edit]

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.[6]

Including gross disproportion means that an ALARP judgement in the UK is not a simple cost benefit analysis, but is weighted to favour carrying out the safety improvement. However, there is no broad consensus on the precise factor that would be appropriate: the HSE recommends that the bias towards safety "has to be argued in the light of all the circumstances applying to the case and the precautionary approach that these circumstances warrant".[7]

Use outside the UK[edit]

The ALARP or ALARA principle is mandated by particular legislation in some countries outside the UK, including Australia, the Netherlands and Norway. Where the ALARP principle is used, it may not have the same implications as in the UK, as "reasonably practicable" may be interpreted according to the local culture, without introducing the concept of gross disproportionality.[8]

The term ALARA, or "as low as reasonably achievable" is used interchangeably in the United States of America. It is used in the field of radiation protection.[9] Its application in the regulation of radiation risk in some areas has been challenged.[10]

Starfish Medical, a company focusing on medical device contract manufacturing and product development, through the Medical Device Directive of Canada is undergoing extensive consideration of the transfer of ALARP to AFAP (“As Far As Possible”) specifically for the regulation of risk of medical devices. The ALARP concept contains legal interpretation of the regulatory process that promotes financial consideration in higher regard than of the requirements of safety and performance of medical devices. Contradicting this approach, AFAP requires that all ventures of safety must be addressed in the intent of the consumer and effectiveness of the product rather than capital gain of the corporation. Under AFAP standards there are two defined justifications for the lack of implementation of risk-preventative measures. The first indicates that the additional risk control will not provide additional support for the system, such as an additional alarm when a previous alarm is functioning. The second states that a risk control system does not have to be implemented if there is a more effective risk control that can not be simultaneously executed due to various scenarios such as spatial boundaries. By implementing this new standard of risk mitigation, companies must demonstrate that they have considered and implemented all necessary means of addressing risk of a product or developed system.[citation needed]

In Australia the Work Health & Safety Act 2011 introduced the term So Far As Is Reasonably Practical (SFAIRP) based on the UK legislation. In some industry sectors the term SFARIP has become the common usage and can be used interchangeably with ALARP, but some people believe that SFAIRP and ALARP are two different legal tests.[11]

Legal challenge[edit]

A two-year legal battle in the European Court of Justice resulted in the SFAIRP principle being upheld on 18 January 2007.[12]

The European Commission had claimed that the SFAIRP wording in the Health & Safety at Work Act did not fully implement the requirements of the Framework Directive. The Directive gives employers an absolute duty "to ensure the safety and health of workers in every aspect related to the work", whereas the Act qualifies the duty "So Far As is Reasonably Practicable". The court dismissed the action and ordered the Commission to pay the UK's costs.[12][13]

Had the case been upheld, it would have called into question the proportionate approach to safety risk management embodied in the ALARP principle.

Carrot diagrams[edit]

Carrot diagram

'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' 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.[14][7]

Carrot diagrams are sometimes known as 'ALARP Triangles'.[15][16][17] 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.

See also[edit]


  1. ^ "ALARP Guidance Note" (PDF). Commonwealth Offshore Petroleum and Greenhouse Gas Storage (Safety) Regulations 2009. NOPSEMA. June 2015. Archived from the original (PDF) on 16 June 2016. Retrieved 20 May 2016.
  2. ^ "ALARP Guidance". UK Health and Safety Executive. Archived from the original on 28 October 2020. Retrieved 29 June 2007.
  3. ^ a b "Reasonably Practicable" (PDF). WorkSafe New Zealand. March 2016. Archived from the original (PDF) on 9 October 2016. Retrieved 7 October 2016.
  4. ^ "The Meaning of Reasonably Practicable" (PDF). Safe Work Australia. 2011. Archived from the original (PDF) on 6 November 2016. Retrieved 7 October 2016.
  5. ^ Yasseri, Sirous (2013). "The ALARP Argument" (PDF). FABIG Newsletter (61). Retrieved 17 July 2023.
  6. ^ Edwards v. National Coal Board. Archived 28 September 2018 at the Wayback Machine (1949) All ER 743 (CA)
  7. ^ a b Reducing risks, protecting people: HSE’s decision-making process (PDF). Sudbury: HSE Books. 2001. ISBN 978-0717621514.
  8. ^ Risk Acceptance Criteria: Overview of ALARP and Similar Methodologies as Practiced Worldwide (PDF) (White Paper). Mary Kay O’Connor Process Safety Center. January 2020.
  9. ^ Kathren RL (December 2002). "Historical Development of the Linear Nonthreshold Dose-Response Model as Applied to Radiation". University of New Hampshire Law Review. 1 (1).
  10. ^ Oakley1, Paul A.; Harrison, Deed E. (April 2020). "Death of the ALARA Radiation Protection Principle as Used in the Medical Sector". Dose-Response. 18 (2): 1559325820921641. doi:10.1177/1559325820921641. PMC 7218317. PMID 32425724.
  11. ^ Robinson, Richard; Francis, Gaye (January 2014). "SFAIRP vs ALARP". CORE 2014: Rail Transport For A Vital Economy. Conference on Railway Excellence. Adelaide: Railway Technical Society of Australasia. pp. 661--668.
  12. ^ a b Judgment of the Court (Third Chamber) of 14 June 2007. Commission of the European Communities v United Kingdom of Great Britain and Northern Ireland, Case C-127/05, ECLI:EU:C:2007:338
  13. ^ Press release Archived 3 December 2008 at the Wayback Machine by the UK Health and Safety Executive
  14. ^ The tolerability of risks from nuclear power stations (PDF) (Report). HMSO. 1992 [1988].
  15. ^ Valeur, Jens R; Petersen, Johannes (13 October 2013). "Use of the ALARP Principle for Evaluating Environmental Risks and Impacts of Produced-Water Discharged to Sea". Oil and Gas Facilities. 2 (6): 92--100. doi:10.2118/167263-PA.
  16. ^ "ALARP : Is the risk as low as reasonably practicable?". BMT. 14 September 2021. Retrieved 24 March 2023.
  17. ^ "As Low As Reasonably Practicable – What Does ALARP Really Mean In Digital Health Compliance?". Safehand Consulting Limited. 31 July 2018. Retrieved 24 March 2023.

External links[edit]