AHBs not interlocked with signals?

[snowball]

Is there a website that explains the rules used to decide what type of level crossing can be used depending on the characteristics of the location and its traffic?

 

[dk1]

Milford is another location that must have a signal inhibited AHB. I've driven a car across the level crossing while a 450 was coming into the platform.

Westerfield (up) Eccles Road/Hargham (dn) Attleborough (dn) Wymondham (dn) Waterbeach (dn) Worstead (up) to name a few also work on this principal for stopping trains only.

 

[GB]

Haughley Junction AHB on the GEML can have a deferred closing operation for some services due to the track and signalling layout. Only when theres multiple trains though.

 

[Joseph_Locke]

Westerfield (up) Eccles Road/Hargham (dn) Attleborough (dn) Wymondham (dn) Waterbeach (dn) Worstead (up) to name a few also work on this principal for stopping trains only.

Haughley Junction AHB on the GEML can have a deferred closing operation for some services due to the track and signalling layout. Only when theres multiple trains though.

Those are probably stopping / non-stopping controls, which just change the point at which the train strikes-in on the AHB system.
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Is there a website that explains the rules used to decide what type of level crossing can be used depending on the characteristics of the location and its traffic?

http://orr.gov.uk/__data/assets/pdf_file/0016/2158/level_crossings_guidance.pdf

 

[Llanigraham]

Then it wasn't an ABCL. max 55 as Railsigns says.

Bromfield LX was an ABCL and is overlooked by Bromfield Signal Box.

Line speed was NOT 55!

 

[Railsigns]

Bromfield LX was an ABCL and is overlooked by Bromfield Signal Box.

That is not an ABCL. Look at the length of that barrier! It's an MCB crossing.

As for being overlooked by the signal box, there's a big clue in the "A" of "ABCL". This stands for "automatic", which means there's no signaller involvement in the crossing's operation.

 

[Joseph_Locke]

That is not an ABCL. Look at the length of that barrier! It's an MCB crossing.

It is indeed MCB

... and ABC agrees.

 

[ComUtoR]

That is not an ABCL. Look at the length of that barrier! It's an MCB crossing.

I'm slightly confused. What has the length of the barrier got to do with it ?


Automatic crossings
Automatic half-barrier crossing AHBC
Automatic barrier crossing locally monitored ABCL
Automatic open crossing locally monitored AOCL
Crossing with red and green warning lights R/G
(also included as a user-worked crossing)

I don't see a any reason why ABCL can't be full barrier. I was always taught that AH is automatic half barrier and AB is full barrier.

Is there a way to find the official type of crossing at a given location ? Sectional Appendix ?
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It is indeed MCB

... and ABC agrees.

Awesome !

 

[Railsigns]

I'm slightly confused. What has the length of the barrier got to do with it ?

It's clearly a full-length barrier that closes off the whole roadway. An ABCL only has half-barriers.

I was always taught that AH is automatic half barrier and AB is full barrier.

You've been taught wrongly.

 

[ComUtoR]

It's clearly a full-length barrier that closes off the whole roadway. An ABCL only has half-barriers.

Does that apply to ALL automatic barriers ?

 

[Railsigns]

Does that apply to ALL automatic barriers ?

Yes it does (currently, at least), unless you count an MCB-OD as an automatic crossing.

 

[ComUtoR]

Cheers.

 

[Joseph_Locke]

Does that apply to ALL automatic barriers ?

Yes*, because an automatic crossing* has no way to tell if there is a road vehicle or pedestrian on the crossing, so an escape route has to be left open - so only half a barrier is fitted.

*except OD, which can tell, so it can have full barriers. Strictly speaking, and OD crossing isn't fully automatic , because the signaller is still involved.
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I was always taught that AH is automatic half barrier and AB is full barrier.

AHB only has an H in it to avoid confusion with AB (absolute block)?

 

[ge-gn]

That is not an ABCL. Look at the length of that barrier! It's an MCB crossing.

Another giveaway would be the lack of "KEEP CROSSING CLEAR" signs on the lightboard posts. MCB for sure.

 

[ComUtoR]

AHB only has an H in it to avoid confusion with AB (absolute block)?

Not a clue to be honest. I can't see why the ABCL can't be called AHBCL. Seems weird to drop the H but that's the railways for ya

 

[Railsigns]

I can't see why the ABCL can't be called AHBCL. Seems weird to drop the H but that's the railways for ya

The automatic crossing designations AOCL, AOCR and ABCL all conform to a consistent pattern. The odd one out is AHBC, which should logically be designated ABCR, although I can't see it ever changing now.

 

[Llanigraham]

Well that was what we residents called it!!

 

[signallerscot]

Well you were wrong. It is categorically, unequivocally an MCB1. It's like calling your Down Home the Up Distant.

 

[Railsigns]

Well you were wrong. It is categorically, unequivocally an MCB1.

It would only be called that in Scotland, though. The numerical categorisation of MCB types was confined to the Scottish Region.
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Well that was what we residents called it!!

You do know that the Sectional Appendix will tell you what type of crossing it is, right? If it is an ABCL, it'll say so. If it's not, it won't.

 

[Class 170101]

Don't forget we also now have AOCL+B too.

AHBs have never been linked to signals & fail in the lowered position. Once this occurs the signaller will eventually stop & caution trains. Line speed applies (up to 100mph) except for wrong direction movements.

Surely AHBs fail in the raised position too? Lights working but barriers up (and possibly barriers up and lights failed)?

 

[Railsigns]

Surely AHBs fail in the raised position too? Lights working but barriers up (and possibly barriers up and lights failed)?

The barriers at AHBCs are specially designed to drop in the event of failure (whereas ABCL barriers will rise).

 

[dk1]

The barriers at AHBCs are specially design to drop in the event of failure (whereas ABCL barriers will rise).

Thank you. I've never been cautioned over a failed AHB & found the barriers raised.

 

[najaB]

Okay, random question after coming across this video on Youtube:
[youtube]UL6C5FmeDU4[/youtube]

As I understand it, an accident like this shouldn't happen in the UK as all crossings are either linked to signalling so presumably the signaller would know about the runaway or have a treadle on the line to cause the barriers to close (note it was a single track line). But what would happen if it was a wrong-way runaway on a dual track line? Would the lights/barriers activate?

 

[Marklund]

Okay, random question after coming across this video on Youtube:
[youtube]UL6C5FmeDU4[/youtube]

As I understand it, an accident like this shouldn't happen in the UK as all crossings are either linked to signalling so presumably the signaller would know about the runaway or have a treadle on the line to cause the barriers to close (note it was a single track line). But what would happen if it was a wrong-way runaway on a dual track line? Would the lights/barriers activate?

Depends on the crossing.
Some older AHBs don't have bidirectional controls, and some do.

 

[Llanigraham]

Unlikely to happen anyway due to our braking system.

 

[edwin_m]

Unlikely to happen anyway due to our braking system.

The air brake used in the UK differs only in detail from that in the US, so an unbraked runaway can happen in either case if, for example, the air brake pipes aren't connected and the hand brakes are not applied.

 

[MarkyT]

Okay, random question after coming across this video on Youtube:

As I understand it, an accident like this shouldn't happen in the UK as all crossings are either linked to signalling so presumably the signaller would know about the runaway or have a treadle on the line to cause the barriers to close (note it was a single track line). But what would happen if it was a wrong-way runaway on a dual track line? Would the lights/barriers activate?

It shouldn't happen in the US either. The film showed a single track so, by definition, it must have had bidirectional controls. So I'm mystified why the lights and barriers didn't activate on approach. It's possible there was something wrong with the crossing or perhaps it was purposely disabled on a section of track out of use or mothballed, of which there's a great deal in the USA.

Depends on the crossing.
Some older AHBs don't have bidirectional controls, and some do.

Yes, on double tracks older AHBs do not have bi-di, but more modern ones do. The strike-in for the reverse direction is usually situated closer in to the crossing than that for the normal direction, so a lower reverse direction approach speed limit is applied to preserve the minimum warning time. Bi-di controls are incorporated today even when the two lines are not otherwise signalled for two way working. This is in order that when temporary single line working with pilotman is implemented, during engineering work for instance, it avoids having to post an additional local operator at the crossing to activate it manually on instruction from the signaller (using the local control unit).

 

[najaB]

It shouldn't happen in the US either. The film showed a single track so, by definition, it must have had bidirectional controls. So I'm mystified why the lights and barriers didn't activate on approach. It's possible there was something wrong with the crossing or perhaps it was purposely disabled on a section of track out of use or mothballed, of which there's a great deal in the USA.

I am not surprised by anything about US rail, especially secondary tracks like that appeared to be. It may even not have automated warnings in both directions if the approach speed was expected to be low from one way.

 

[Marklund]

Unlikely to happen anyway due to our braking system.

On track plant has a habit of runaways

Again, and again and again not to forget this tragedy

 

[GB]

This was posted last week too.

https://www.gov.uk/government/publications/safety-digest-012017-toton-sidings


Runaway loco.