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combined level crossing flashing lights and traffic lights
#1
Hi Signalling Engineer:

Recently, I am just reading the "introduction to railway signalling" book the part that describing the level crossing and I remembered I have seen the photo of combined flashing lights and traffic lights on the same post that someone has showed me before. Since I am not familiar with combined installation, I have questions such as

1. is the driver be more likely to obey the flashing lights or the traffic lights (personally, I think the driver would be more likely to obey the flashing light since it 'flashes' and attract the driver attention) I'm not sure whether I am right for this ?

2. is there any human factors behind this ? and how can a signal design engineer take this into the level crossing design ?





thanks



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#2
It'd be good to see this photo; I really can't think of one in the UK. Even where there is a level crossing very close to a crossroads wich necessitates interlocking between the road traffic lights and the crossing I do not visualise the "wig-wags" on the same post as the traffic lights.

I can't find anything in the book itself which you mention..

1. Certainly it could easily confuse a driver to be presented by a green traffic light and flashing red wig-wags. Let's hope they do obey the latter. Really can't understand what circumstances would make this a sensible arrangement. Note that in the UK a police officer has the authority to give permission for a driver to pass a red traffic light, but NOT flashing red wig-wags (because these are used to protect AHBC and this could be a very dangerous thing to do)

2. I'd certainly hope that anyone who decided to produce such an arrangement would have submitted to a Human Factor's Assessment.

Anyone else aware of such installations- I guess not in the UK but elsewhere......


(06-04-2011, 12:44 PM)onestrangeday Wrote: Hi Signalling Engineer:

Recently, I am just reading the "introduction to railway signalling" book the part that describing the level crossing and I remembered I have seen the photo of combined flashing lights and traffic lights on the same post that someone has showed me before. Since I am not familiar with combined installation, I have questions such as

1. is the driver be more likely to obey the flashing lights or the traffic lights (personally, I think the driver would be more likely to obey the flashing light since it 'flashes' and attract the driver attention) I'm not sure whether I am right for this ?

2. is there any human factors behind this ? and how can a signal design engineer take this into the level crossing design ?





thanks

PJW
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#3
Hi PJW:

thanks your reply. I guess probably different countries have different approach. Since I'm not experienced in combined installation for signals, what are the main consideration and things need to pay attention to the combined installation ?







(06-04-2011, 06:33 PM)PJW Wrote: It'd be good to see this photo; I really can't think of one in the UK. Even where there is a level crossing very close to a crossroads wich necessitates interlocking between the road traffic lights and the crossing I do not visualise the "wig-wags" on the same post as the traffic lights.

I can't find anything in the book itself which you mention..

1. Certainly it could easily confuse a driver to be presented by a green traffic light and flashing red wig-wags. Let's hope they do obey the latter. Really can't understand what circumstances would make this a sensible arrangement. Note that in the UK a police officer has the authority to give permission for a driver to pass a red traffic light, but NOT flashing red wig-wags (because these are used to protect AHBC and this could be a very dangerous thing to do)

2. I'd certainly hope that anyone who decided to produce such an arrangement would have submitted to a Human Factor's Assessment.

Anyone else aware of such installations- I guess not in the UK but elsewhere......


(06-04-2011, 12:44 PM)onestrangeday Wrote: Hi Signalling Engineer:

Recently, I am just reading the "introduction to railway signalling" book the part that describing the level crossing and I remembered I have seen the photo of combined flashing lights and traffic lights on the same post that someone has showed me before. Since I am not familiar with combined installation, I have questions such as

1. is the driver be more likely to obey the flashing lights or the traffic lights (personally, I think the driver would be more likely to obey the flashing light since it 'flashes' and attract the driver attention) I'm not sure whether I am right for this ?

2. is there any human factors behind this ? and how can a signal design engineer take this into the level crossing design ?





thanks

Reply
#4
(06-04-2011, 06:33 PM)PJW Wrote: It'd be good to see this photo; I really can't think of one in the UK. Even where there is a level crossing very close to a crossroads wich necessitates interlocking between the road traffic lights and the crossing I do not visualise the "wig-wags" on the same post as the traffic lights.

I can't find anything in the book itself which you mention..

1. Certainly it could easily confuse a driver to be presented by a green traffic light and flashing red wig-wags. Let's hope they do obey the latter. Really can't understand what circumstances would make this a sensible arrangement. Note that in the UK a police officer has the authority to give permission for a driver to pass a red traffic light, but NOT flashing red wig-wags (because these are used to protect AHBC and this could be a very dangerous thing to do)

2. I'd certainly hope that anyone who decided to produce such an arrangement would have submitted to a Human Factor's Assessment.

Anyone else aware of such installations- I guess not in the UK but elsewhere......

I'm in the same camp as you. The only thing that I can think this refers to is the Mk1 Penguin barriers that had the concrete post with the barrier support and motor combined on the same unit that held the road lights.

Peter
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#5
What is often forgotten that a red light and a flashing red light have very different legal meanings to a driver (road in this case). A steady red can be passed under certain circumstances, i.e. emergency services. Flashing red prohibits anyone from passing it under any circumstance!

There are many installations in the UK where rail signalling and road traffic control are cut into each other. Look at most metros with on street sections. I believe it is NET that actually has a length pass through the centre of a large roundabout! As for wig-wags and traffic lights on the same post, I seem to remember one at North Pole for a non-public road crossing at a very acute angle to the railway.

Jerry
Le coureur
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#6
I have attached the photo for discussion and clarity.


I am wondering does the car drivers are more likely to obey the flashing lights or the traffic lights(personally, I think the driver would be more likely to obey the flashing light since it 'flashes' and attract the driver attention----in other words, flashing lights are more effective than the traffic lights) I'm not sure whether I am right for this ?
what might be the human factors behind this ? How could level corssing control desgin take theses issues into account ?

Beside, what are reasons for this kind of combined installation ???
I think wouldn't be better to install separatley !!










(07-04-2011, 09:17 AM)Jerry1237 Wrote: What is often forgotten that a red light and a flashing red light have very different legal meanings to a driver (road in this case). A steady red can be passed under certain circumstances, i.e. emergency services. Flashing red prohibits anyone from passing it under any circumstance!

There are many installations in the UK where rail signalling and road traffic control are cut into each other. Look at most metros with on street sections. I believe it is NET that actually has a length pass through the centre of a large roundabout! As for wig-wags and traffic lights on the same post, I seem to remember one at North Pole for a non-public road crossing at a very acute angle to the railway.

Jerry

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#7
Thanks for that; VERY interesting.
Any clue where in the world?
Certainly not in the UK and I very much doubt we'd allow it for very much the reasons you mention.

Obviously English speaking, drive on the left, some American influence...... Not likely to be India nor Thailand; don't think it is Singapore, so could it be New Zealand perhaps ?


(07-04-2011, 12:28 PM)onestrangeday Wrote: I have attached the photo for discussion and clarity.


I am wondering does the car drivers are more likely to obey the flashing lights or the traffic lights(personally, I think the driver would be more likely to obey the flashing light since it 'flashes' and attract the driver attention----in other words, flashing lights are more effective than the traffic lights) I'm not sure whether I am right for this ?
what might be the human factors behind this ? How could level corssing control desgin take theses issues into account ?

Beside, what are reasons for this kind of combined installation ???
I think wouldn't be better to install separatley !!

PJW
Reply
#8
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
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#9
Only hit I get on the "Black and White Cleaning" company is Australia. losler's answer is far more conclusive though.
Le coureur
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#10
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?

(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
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