[SystemSafety] MISRA publishes Guidelines for Automotive Safety Arguments

[Martyn Thomas]

On 27/09/2019 16:46, Derek M Jones wrote:

> How does anybody figure out where "so far as is reasonably practical"

HSE says:

/The definition set out by the Court of Appeal (in its judgment in
Edwards v. National Coal Board, [1949] 1 All ER 743) is:/

//

/“‘Reasonably practicable’ is a narrower term than ‘physically possible’
… a computation must be made by the owner in which the quantum of risk
is placed on one scale and the sacrifice involved in the measures
necessary for averting the risk (whether in money, time or trouble) is
placed in the other, and that, if it be shown that there is a gross
disproportion between them – the risk being insignificant in relation to
the sacrifice – the defendants discharge the onus on them.”/

//

/In essence, making sure a risk has been reduced ALARP is about weighing
the risk against the sacrifice needed to further reduce it. The decision
is weighted in favour of health and safety because the presumption is
that the duty-holder should implement the risk reduction measure. To
avoid having to make this sacrifice, the duty-holder must be able to
show that it would be grossly disproportionate to the benefits of risk
reduction that would be achieved. Thus, the process is not one of
balancing the costs and benefits of measures but, rather, of adopting
measures except where they are ruled out because they involve grossly
disproportionate sacrifices. Extreme examples might be:/

//

  * /To spend £1m to prevent five staff suffering bruised knees is
    obviously grossly disproportionate; but /
  * /To spend £1m to prevent a major explosion capable of killing 150
    people is obviously proportionate./

//

/Of course, in reality many decisions about risk and the controls that
achieve ALARP are not so obvious. Factors come into play such as ongoing
costs set against remote chances of one-off events, or daily expense and
supervision time required to ensure that, for example, employees wear
ear defenders set against a chance of developing hearing loss at some
time in the future. It requires judgment. There is no simple formula for
computing what is ALARP./


There's more detail on how HSE expects its inspectors to apply the law
here:  http://www.hse.gov.uk/risk/expert.htm



HSWA explicitly says
<https://www.legislation.gov.uk/ukpga/1974/37/section/40> that the
burden of showing that a risk has been reduced SFAIRP falls on the
person who seeks to rely on it.

*40 Onus of proving limits of what is practicable etc.**
*
/In any proceedings for an offence under any of the relevant statutory
provisions consisting of a failure to comply with a duty or requirement
to do something so far as is practicable or so far as is reasonably
practicable, or to use the best practicable means to do something, it
shall be for the accused to prove (as the case may be) that it was not
practicable or not reasonably practicable to do more than was in fact
done to satisfy the duty or requirement, or that there was no better
practicable means than was in fact used to satisfy the duty or
requirement.//
/
Martyn

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