Some Specific Activities at the Railway Signalling System Development

Influence of Distributed SRCS Architectures on Dependability and Safety of Realised Safety Functions

“…In this case we have to assume more pessimistic approach of evaluation, and dangerous failure rate is therefore assumed as a sum of separately determined dangerous failure rate of each realised SF. This issue is described in [5].…”

“…More safety functions can be realised by this SRCS. When we assume, that dangerous failure of any element which cooperates on realisation of safety function will cause dangerous failure of SF (we can assume serial model of system elements), then dangerous failure rate can be express using equation: , (5) where is dangerous failure rate of element i which cooperate on SF realisation and n is count of elements which realises SF. When SRCS is realising multiple SF, it is obvious that some elements (such as control logic) will be used to realize more than one SF.…”

“…In case that SF1 and SF2 are realised, dangerous failure rate can be determined by (5), what is given by serial model of used components for SF realisation. To the serial model must be included communication dangerous failure rate.…”

“…. (11) Danger failure rate of SFK can be determined also by (5). It is important to assume all used elements in each way of communication because of fact, that each element providing information transfer (in first and also second way) can cause danger state.…”