"moving block, distance to go" signalling system

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Sprog

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Moving Block is the system they where going to use on the WCML before they realised it was all pie in the sky!
 

Met Driver

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There's a fair bit of info here (haven't read it myself yet :oops:).

I'm pretty sure one TN is correct in saying it is some sort of "in cab" system though.
 

Tomnick

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I suspect (but don't actually know!) that it's based on each train maintaining a safe 'envelope' in front of itself, taking into account gradients and weight - if the train in front comes within this distance, the train will set a lower 'speed limit' to shorten the envelope required. It all seems very efficient (trains can run at 'braking distance' apart, as opposed to a minimum of length of block section plus braking distance on a fixed block system), but it's also all very impractical ;) .
 
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Tom

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It's actually very alike to the ATO systems running on the Victoria and Central Lines. The Distance To Go system on the Vic uses code pulses (those being 420 pulses for next 2 blocks available, etc).

The Central uses a format slightly different, but is based on that principle. Same with the DLR too.
 

Tomnick

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I was under the impression that all of these systems are, in fact, fixed block as opposed to moving block?
 

Sprog

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Tomnick said:
I suspect (but don't actually know!) that it's based on each train maintaining a safe 'envelope' in front of itself, taking into account gradients and weight - if the train in front comes within this distance, the train will set a lower 'speed limit' to shorten the envelope required. It all seems very efficient (trains can run at 'braking distance' apart, as opposed to a minimum of length of block section plus braking distance on a fixed block system), but it's also all very impractical ;) .
Tomnicks spot on..........thats exaclty what it is..........

Its all done by GSM radio signals. As i said, moving block was to be the principal used on the WCRM, but Railtrack where under false hope, and when they reaslied it wasnt going to happen, they had no choice but to compromise by using traditional signalling = No 140mph. ETRMS (or whatever it is) stage 3 ( :?: ) uses moving block principal. Basically moving block is precisly that - A virtual 'safe' zone in which the train travels in.
 

ChrisCooper

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The main difference is that distance to go is fixed block, wheras moving block is moving block (shocking stuff :shock: ). Both are forms of ATP or ATO. The latter is more suited to high capacity metro lines where all trains are fitted with the system and have similar, or better, identical performance, and is very suited to ATO. The former is just an anhanced for of ATP, which rarther than using a blocks to go system like BR-ATP or TVM, it tells the driver or train exactly how far until it needs to stop. One of the big differences is the accuracy of information on train speeds and positions. DTG pretty much works like a block based system but using small blocks, and can still use track circuits. Moving block on the other hand needs very presise data about the exact position and speed of the train infront. One big issue, that often makes moving block unviable, is that it's difficult to integrate into existing signalling systems, which is essential if trains are going to run that arn't fitted with the system. This would have been a problem on the WCML, since to make it viable all trains, not just the Pendolinos, would have had to be fitted. If not, you end up reverting to a normal, fixed block system around none fitted trains, since these neither have the ability to tell the system where they are, or to tell how far ahead the train infront is. It only really fitted with Bransons original idea of a totally segregated 140mph railway for his Pendolinos.
ETRMS actually offers all 3 ATP systems. Level one is a basic blocks to go system, which can work with or without lineside signalling (they could be replaced with TVM style section markers, although again it means all trains must be fitted), level 2 is distance to go, and level 3 is moving block. Level one has been critisised for reducing capacity over conventional signalling, and level 3 is expensive, un-practical on a mixed system and mostly unnecasery, so level 2 is the most likely option to be fitted, and AFAIK this is what is going to be tested on the Cambrian Coast.
140mph running though wasn't dependant on moving block, just cab signalling, so hopefully once ETRMS is fitted, the WCML will finally have 140mph running, along perhaps with the ECML (by the time it happens, the 91s and Mk4s will be up for replacement, and I'm sure the replacements will be 140mph capable at least.
 
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