01-03-2011, 03:39 PM
Pink fluffy SIL0 (PFS0) humans are the primary actors within a system. PFS0s make mistakes. Rules and processes don't stop PFS0s from making errors but provide a framework which when adhered too should provide 'a' level of safety.
It seems incredible how a function such as BGocc then BGclr and 42 replaced (BG is the track over the LX and 42 the relevant stop signal) which would lock 1 (gate lock) when 42 cleared had not been included in a fail safe system. The Hull Paragon accident (14th February 1927) details that system failure due to poor design can, and will, eventually occur.
For me, there is a fine line between the cost savings required by engineering versus the level of safety these systems must provide. Deadlines and timescales can also affect the delivered result. Savings are often short term 'gains' where the long term affects outweigh any reduction in costs. Human factors should always be considered and incorporated. However, the assessment should be based upon safety and system integrity.
My personal view is that the system failed the signaller. Whilst a mistake was made, the results were unfortunately fatal. The addition of electric locks to level 1 would have been minor changes but the rail industry often seems to choose not to question why something is the way it is. Many accidents of a similar nature have occured previously and yet a system that failed to identify predictable errors was commissioned and it took 34 years for the failure to occur/become apparent.
Jerry
It seems incredible how a function such as BGocc then BGclr and 42 replaced (BG is the track over the LX and 42 the relevant stop signal) which would lock 1 (gate lock) when 42 cleared had not been included in a fail safe system. The Hull Paragon accident (14th February 1927) details that system failure due to poor design can, and will, eventually occur.
For me, there is a fine line between the cost savings required by engineering versus the level of safety these systems must provide. Deadlines and timescales can also affect the delivered result. Savings are often short term 'gains' where the long term affects outweigh any reduction in costs. Human factors should always be considered and incorporated. However, the assessment should be based upon safety and system integrity.
My personal view is that the system failed the signaller. Whilst a mistake was made, the results were unfortunately fatal. The addition of electric locks to level 1 would have been minor changes but the rail industry often seems to choose not to question why something is the way it is. Many accidents of a similar nature have occured previously and yet a system that failed to identify predictable errors was commissioned and it took 34 years for the failure to occur/become apparent.
Jerry
Le coureur