A short and pragmatic guide on how to demonstrate what is practical and reasonable in complying with the ALARP safety goal
The principle of As Low As Reasonably Practical (ALARP) is enshrined in the Health and Safety legislation of many western countries and embodies a hybrid rights and utility (cost/benefit) decision strategy used to determine when to stop reducing risk associated with the use of a system. (1),(2)
To quote the UK Defence safety standard DEF-STAN 00-56 ALARP is achieved when:
… it has been demonstrated that the cost of any further risk reduction, where the cost includes the loss of system capability as well as financial or other resource costs, is grossly disproportionate to the benefit obtained from that risk reduction. (DEF-STAN 00-56 Issue 3)
Unfortunately the terms reasonable and practical are unbounded qualifiers of the requirement, what is deemed to be either reasonable or practical is inherently subjective and subject to interpretation. This of course is not a good thing when it comes to writing a specification or forming a contract so from this perspective while ALARP may be a laudable societal goal but it is not a good commercial requirement. Further what do you do in practical terms when a naive customer requires you to ‘demonstrate’ the achievement of ALARP for all risks no matter how many of them, or how well they are understood?