Level Crossing Sequence

[greataj]

A very specific detail I've recently observed at a number of level crossings I can't say I've noticed before is that once the amber light illuminates (approx 3 seconds) both red lights then breifly flash together, before going to their usual independant flashing "wig-wag" sequence. Is this actually a standard, official thing and if so, has it always been the case?

 

[Y Ddraig Coch]

As far as I'm aware they all do that.

 

[swt_passenger]

Yes, it’s normal, and for examples you can see it happening on numerous YouTube videos of crossings.

 

[Y Ddraig Coch]

The link below to some videos of level crossings does seem to back up my thoughts also.

 

[greataj]

Yes that's exactly it, so must be pretty standard. I guess it's an attempt to alert greater driver attention to stop maybe.

 

[satisnek]

Not all of them do it. Look at No.7 in the above video, where the red lights start straight away as wig-wag. This crossing still has old-fashioned bulbs and presumably still has an entirely electromechanical control system. So it would appear to be a fairly new thing.

I observed something strange at Findern AHBC recently. The lights extinguished before the barriers were fully raised (as they do in the video) and then both reds briefly flashed simultaneously when the barriers hit their upper end stops. Does this happen very often?

 

[swt_passenger]

I observed something strange at Findern AHBC recently. The lights extinguished before the barriers were fully raised (as they do in the video) and then both reds briefly flashed simultaneously when the barriers hit their upper end stops. Does this happen very often?

We also had a thread about that scenario back in November, so it‘s possible it can occur elsewhere.

AHBC crossing question.

One for anyone with knowledge of the technical operation of Automatic Half Barrier Level Crossings. A level crossing I regularly use of this type and one where I often observe trains pass appears to have a ‘quirk’ which I’ve never noticed anywhere else. When observing the crossing operation...

www.railforums.co.uk

 

[edwin_m]

Not all of them do it. Look at No.7 in the above video, where the red lights start straight away as wig-wag. This crossing still has old-fashioned bulbs and presumably still has an entirely electromechanical control system. So it would appear to be a fairly new thing.

Could be that it does happen, but is shorter than the time the bulbs take to heat up enough to emit light.

 

[satisnek]

We also had a thread about that scenario back in November, so it‘s possible it can occur elsewhere.

AHBC crossing question.

One for anyone with knowledge of the technical operation of Automatic Half Barrier Level Crossings. A level crossing I regularly use of this type and one where I often observe trains pass appears to have a ‘quirk’ which I’ve never noticed anywhere else. When observing the crossing operation...

www.railforums.co.uk

Ah, thanks for that, I can actually remember reading this but by the time I saw the phenomenon for myself a few weeks later it had fallen out of my brain

Could be that it does happen, but is shorter than the time the bulbs take to heat up enough to emit light.

I don't think so, because other crossings using bulbs are shown where they do both illuminate at the start. I'm fairly certain that red level crossing lights used to do nothing more than flash alternately - which can be reproduced with the classic astable multivibrator circuit although an electromechanical device was most likely used on earlier crossings. I don't know when the 'both lights on at start' sequence was first implemented, but it probably predates LEDs.

 

[Annetts key]

A very specific detail I've recently observed at a number of level crossings I can't say I've noticed before is that once the amber light illuminates (approx 3 seconds) both red lights then breifly flash together, before going to their usual independant flashing "wig-wag" sequence. Is this actually a standard, official thing and if so, has it always been the case?

It depends on which type of flasher unit is in use. The relay and electro-mechanical types don't ever illuminate both red lights at the same time (except if it fails internally but then it tends not to flash at all). And IIRC the first generation of electronic flashers didn't illuminate both red lights at the same time.

However, the current design of flasher does do as described, when first activated it illuminates both red lights at the same time and then flashes them in the normal way.

Oh, and the wig-wag light units were originally 24V 36W filament lamps. Then they moved to 24V 50W quartz halogen type. And now LED type are available.

If an installation was upgraded to 24V 50W quartz halogen type or this was a new installation, a modern flasher unit had to be fitted, because the older design was not specified for this lamp type.