(26-09-2009, 04:28 PM)oxfordjack Wrote: How do you do.
Can you give me some hints how to answer that question?
Thank you
Classic "risk" question which is very similar to what can come up in module 1; so approach it similarly. Split it down:
a) What is the chance / likelihood of a SPAD occuring at that particular signal
b) What would be the consequences of a SPAD if it did occur?
For part a) you could use a FAULT TREE (see IRSE News article earlier this year)
For part b) you could use an EVENT TREE (see link Peter gave)
Also inviting you to explain what you understand as a tolerable risk and how you would determine that in a particulr situation the risk was suitably low to be under that threshold.
So if you know your "Yellow Book" then you would be well on the way of answering this question- so overall my hint would be STUDY THE BOOK!
What you also need to know to fully answer this questionis how the basic theoretical process is actually applied in the particular scenario described; fundamentally need to describe the process used to "get the applicable numbers" that are used to weight the various scenarios. Ask yourself how the risk profile is affected by having a reduced length overlap and what the motivation for having a shorter than standard length overlap would be. Ask yourself whether there are any mitigations that would be associated with the shorter length.
PJW