01-04-2016, 01:10 PM
@soylemezv
We need to be careful mixing the words safety, availability and cost.
As PJW states, you can of course estimate availability and that should be completed during the conceptual and rerun during the design phases of the scheme. Generally, but not always, higher availability means increased cost.
High availability does not infer a system is safe or the cost is high. Often, the more complex a system is; which infers cost, decreases reliability and availability.
Safety is also not implicit in highly available systems.
However, the rail system or signalling and control systems we build tend to have a relatively high cost, are highly available and safe. Just look at the fallout from the Hatfield Colliery slip or the failure of the Dawlish infrastructure for how third parties have affected the availability of the railway system.
Going back to the original question: fallback systems depend upon the client's requirements. Working at reduced speeds to line of sight is free and relatively safe. It is possible to have a duplicate of the original system that costs the same as the original system but also bumps up costs such as maintenance.
Jerry
We need to be careful mixing the words safety, availability and cost.
As PJW states, you can of course estimate availability and that should be completed during the conceptual and rerun during the design phases of the scheme. Generally, but not always, higher availability means increased cost.
High availability does not infer a system is safe or the cost is high. Often, the more complex a system is; which infers cost, decreases reliability and availability.
Safety is also not implicit in highly available systems.
However, the rail system or signalling and control systems we build tend to have a relatively high cost, are highly available and safe. Just look at the fallout from the Hatfield Colliery slip or the failure of the Dawlish infrastructure for how third parties have affected the availability of the railway system.
Going back to the original question: fallback systems depend upon the client's requirements. Working at reduced speeds to line of sight is free and relatively safe. It is possible to have a duplicate of the original system that costs the same as the original system but also bumps up costs such as maintenance.
Jerry
Le coureur