Re: [SystemSafety] EN 50126/28/29 and MIL STD 882C - Differences

From: Matthew Squair < >
Date: Tue, 14 Apr 2015 20:45:06 +1000

Hi Miriam,

Just on your last point, nope the dollar values or risk levels don't really correlate with SILs. The risk assessment backing those divisions is pretty high level, better to think of it as a high level organisational decision criteria (applied by the U.S. DoD) as to when it's appropriate in cost vs benefit terms to have a formal costed program where you pay for assurance products. Really it's more at the level of the program manager sniffing the air.

Note that just because you don't impose 882 on contract doesn't mean there's nothing done, but 882 when imposed does give the acquirer visibility, a broad framework and 'paid for' assurance products related to contractor efforts.

Matthew Squair

MIEAust, CPEng
Mob: +61 488770655
Email; Mattsquair_at_xxxxxx

On 14 Apr 2015, at 8:24 pm, M Mencke <menckem_at_xxxxxx

Dear all,

I was wondering if anybody has experience in the application of MIL STD 882C in the railway sector, and if there are any major differences between the application of the EN 50126/28/29 standards and this standard.

I do not want to (re) open a discussion about probabilistic risk assessment, but as far as I can see, one of the differences is that THR is not applied. However, occurrence of hazard categorization may be measured qualitatively or quantitatively, EN 50126 calls it "frequence of occurrence of hazardous events", whereas MIL STD 882C calls it "Hazard Probability Levels".

Appendix A provides guidelines for implementation of system safety program requirements, there is a matrix for "Small Dollar or Low Risk Program", "Medium Dollar or Average Risk Program" and "Large Dollar or High Risk Program", I was wondering if the first two programs could be considered approximately equivalent to SIL 1 and SIL 2 according to the EN standards, and the latter equivalent to SIL 4, but I understand that this would be a generalization.

Kind regards,


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