Very much so, thanks for the link. From the aerial photo I am certainly convinced that it is very probably the actual crossing.
It was a bit of a long shot from London, so although I may have been many many miles out it really wasn't too bad an attempt. I admit I was labouring under the misapprehension (having never visited and having better things to do than watch "Neighbours") that Australia drove on the right- otherwise I may have guessed there instead. So we have all learnt something.
So if we take laura's description and assume that there is an "outer strike-in" type feed from the railway to interrupt the traffic light sequence then I agree that the lights should show red no later than when the flashing wigwags start. Raises a couple of questions:
a) what is the required SIL for that function?
b) what about the failure mode in which the wigwags are started because the RER drops (a rightside failure) despite there being no approaching train? Indeed what if the crossing is put into local control?
Think through what the hazards are and do a risk assessment. Decide what are the options for mitigation and determine which should be adopted. Could form quite a good Module 1 question.
Whilst thinking along those lines, how much confidence can we place in the signaller's ability to study CCTV picture of the crossing and correctly give the crossing clear. I guess that it would be no better than 99.9%. What is that in terms of SIL?
It was a bit of a long shot from London, so although I may have been many many miles out it really wasn't too bad an attempt. I admit I was labouring under the misapprehension (having never visited and having better things to do than watch "Neighbours") that Australia drove on the right- otherwise I may have guessed there instead. So we have all learnt something.
So if we take laura's description and assume that there is an "outer strike-in" type feed from the railway to interrupt the traffic light sequence then I agree that the lights should show red no later than when the flashing wigwags start. Raises a couple of questions:
a) what is the required SIL for that function?
b) what about the failure mode in which the wigwags are started because the RER drops (a rightside failure) despite there being no approaching train? Indeed what if the crossing is put into local control?
Think through what the hazards are and do a risk assessment. Decide what are the options for mitigation and determine which should be adopted. Could form quite a good Module 1 question.
Whilst thinking along those lines, how much confidence can we place in the signaller's ability to study CCTV picture of the crossing and correctly give the crossing clear. I guess that it would be no better than 99.9%. What is that in terms of SIL?
(08-04-2011, 07:21 AM)losler Wrote: This looks like an Australian railway. The road traffic lights are interconnected with the railway crossing lights and get a indication from the railway controls about the same time as a 'next train coming' indication for the traffic light to stop their cycle and put all lights back to red to hold the traffic. Therefore the road traffic lights will never show a green when the level crossing lights are flashing.
In my understanding they are used over normal railway crossing lights where there is a road intersection close to the crossing where traffic can easily be controlled to a stop around the crossing using the road traffic light cycles, and therefore cars wanting to turn right at that intersection on the photo will never queue across the level crossing.
Hope this helps
Laura
Looking at those photos again I think that is Geebung station, one of the northern suburbs of Brisbane, QLD and down the road from where I live!
An aerial view of Geebung Level Crossing
http://www.nearmap.com/?ll=-27.368969,15...d=20110323
PJW