TVM Block Marker Boards on the Elizabeth Line.

[MOONY]

Apologies if this has been raised before. At the departure end of each Elizabeth Line station there is a TVM BMB but immediately in advance of it it there is another BMB annotated as "CA" which I presume to mean Co- actor.

Could some kind person explain the significance of this arrangement please?

Many thanks.

Moony

 

[Watershed]

I would presume the CA marker block is there in case a driver has to drive their train through the core manually, to assist them with their stopping position. It does seem a bit of an anachronism, though, given that you are inherently talking about in-cab signalling which shouldn't require any sighting!

 

[zwk500]

Apologies if this has been raised before. At the departure end of each Elizabeth Line station there is a TVM BMB but immediately in advance of it it there is another BMB annotated as "CA" which I presume to mean Co- actor.

Could some kind person explain the significance of this arrangement please?

Many thanks.

Moony

On a technical point, Crossrail doesn't use TVM but a Siemens CBTC system. Although yes the Block Markers are identical.

From the cab ride video, I would guess that the actual board is located at the place by which trains must stop, however because the board is mounted low down for clearance, a co-acting board is provided behind it so that drivers can see the Block Marker Number clearly.

 

[Railsigns]

There's a photograph of a co-acting block marker on this webpage.

CBTC block marker number XR336 on the Crossrail Eastbound line at Custom House station. A smaller 'co-acting' block marker, numbered XR336CA, is provided a short distance beyond for the benefit of drivers of trains standing very close to the primary marker.

 

[MOONY]

Many thanks guys!

Moony

 

[D365]

Argh. Too many abbreviations!

 

[zwk500]

Argh. Too many abbreviations!

Apologies:
TVM - Transmission Voie-Machine (French in-cab signalling, works through coded track circuits)
BMB - Block Marker Board (replaces signals for in-cab signalling)
CA - Co-acting (as stated)
CBTC - Communications Based Train Control (A technical subset of in-cab signalling over radio)

 

[kevin_roche]

I would presume the CA marker block is there in case a driver has to drive their train through the core manually

That is correct. The failure mode is to use ETCS with the driver manually controlling the train when CBTC is not working.