How to replace old signalling systems with track circuit block signalling?

[Mariculous]

Yesterday, track circuit block signalling was introduced on my server, so i started replacing absolute block signalling by track circuit block signalling on most of my lines, as it makes presignalling much less cryptic, thus providing higher speeds and capacity on most lines.

However, there are some cases where I don't know how to replace old signals.
1. Tunnels:
I have a few stations in a tunnel. It seems that there are no track circuit tunnel signals, or at least not yet. How do I properly signal these? I tried to use absolute block at these stations but I am not quite sure if this is the intended usage.

2. Single tracked dead end sections:
I have a few tracks with single tracked dead end tracks with some stations on the single tracked section, currently using token block signalling.
I don't think there is a track circuit replacement for these tracks, is it?

Additionally the help text in the wiki is a bit missleading. It states the following:

- Trains will make a directional reservation (shown in blue in the block reservation display) when they reserve through a section containing bidirectional signals
- The directional reservation ends at the next one way sign

At a dead end track, given that description, I would expect the train to start a directional reservation to the dead end and back, which would cause a directional reservation in both directions, or the way back overriding the other.
The help text should mention that a reservation will always end if the train reverses on its line.

However, it sounds logical to me to me that a directional reservation in both directions would allow exactly one train (the train that created the reservation) to enter that block creating a "normal" reservation up to the tile where, the last single tracked tile and a directional reservation ahead, as any other trains are not permitted in the one direction nor they are in the other direction to enter that single tracked section.
However, I don't know if this would still be automatic-/ track circuit block working method.
I have read about "One train working (without train staff)", which also seems to be some kind of automatic block working.
Additionally, the last section of this https://en.wikipedia.org/wiki/Automatic_block_signaling#Single-direction_ABS also sounds like automatic block signaling allowed through tracks to be used as dead end tracks when a train dispatcher allowed for this.
However, I don't know if this is specific to the US or also used in the UK.

[Rollmaterial]

1. It is true that there are no underground track circuit block signals when the semaphore power signals are introduced in Pak128.Britain-Ex. You need to wait a couple of years for the electro-pneumatic signals to be introduced.
2. Dead-end sections should be signalled with one train staff, not token block. Token block and bidirectional track circuit block signals are meant for single track sections between two passing opportunities. In terms of how the game logic works, a train will always revert to drive by sight upon reversing unless it is in the one train staff working method.

[Mariculous]

Well I used one train staff very often at the beginning, however I don't like it anymore since it always produced deadlocks for some reasons. Some of them have been reported as a bug, some of them could not be reproduced by me yet, so these are not yet reported. For example trains in one train staff working method sometimes passing the one train staff exit without resetting to drive by sight, which is very likely to deadlock the whole network.

Since I had lots of issues with deadlocking one train staff, I replaced all one train staffs with token blocks, which works fine for years now.
Well, token block also has its bugs but as long as you never ever leave a token block at a signal that is placed on a station tile, it's all right.
Also, when in token block, trains won't revert to drive by sight unless they pass a drive by sight sign or one uses block reservation tool to reset the reservation.
At least this is what I have experienced.

Back to track circut block as a replacement for older systems, can I summarize it the following way?
Track circuit block can always be used as a replacemement for absolute block, by simply replacing any absolute block signal by their automatic eqiuvalent, if available, that means
Semaphore stop->Automatic semaphore stop
Semaphore permissive block->Automatic semaphore stop (permissive)
Semaphore combined->Automatic semaphore combined
Semaphore distant->Automatic semaphore distant
Semaphore choose->Automatic semaphore choose

For tunnels, this means no replacement yet but mixing both using track circuit block on the ground and absolute block under ground is not a problem.

Replacing signalling on single tracked token block controlled sections by track circuit block can be done in some cases.
It is possible, if the infrastructure behind the token block is capable of handling multiple trains leaving that block, as there won't be any check if a train entering that section can leave it.
If there are stations on the single tracked sections, these need an exit signal and there has to be a bidirectional signal at both ends of the single tracked section to create a directional reservation.

[jamespetts]

The one train staff working method should suffice when the single line dead end section has only the one platform/siding at the end. However, when there is a single track section with multiple platforms/sidings at the end, or a depot anywhere along its length, you will need to use track circuit block. Track circuit block signals are intended to replace token block signals. Use the bidirectional signals (a signal facing in both directions) on the bidirectional track for this to work.

I do intend to produce videos about token block and track circuit block at some point, but I am not realistically able to produce videos until I am able to upgrade my computer, and my computer upgrade has been delayed again as the part for which I am waiting will now not be available until November.

[Mariculous]

The one train staff working method should suffice when the single line dead end section has only the one platform/siding at the end.

What exactly do you mean with a "single line dead end section [that] has only one platform/siding at the end"?
Do you mean there can be only one station in a single tracked section, when one train staff controlled or do you mean that each station can only have one track, that means no intermediate junctions?
If you mean the latter, I would not even call such a setup a single tracked dead end track.
If you mean the former, then I must admit I have used the one train staff cabinet wrong. However, I would expect both to work to be honest, as long as there is only a single entry and a directly adjacent exit of this whole section.
In the former, deadlocks will randomly occur when used with in combination with any other working method other than drive_by_sight on the  double tracked section.
e.g.
---c=====a
, where "-" is a single track, "c" are two one train staff cabinets on the double tracked section, one at the entry, the other one at the exit, "=" is a double tracked section and "a" is an absolute block signal in the left direction.

Track circuit block signals are intended to replace token block signals. Use the bidirectional signals (a signal facing in both directions) on the bidirectional track for this to work.

Well that's interessting! I tried it out but didn't expect it to work at dead end tracks to be honest and it didn't.
However, I am not quite sure if my used setup was the same as thoe one you explained. I had some experimentation with it early on, so I'll give it another try.

What I had observed is that a train entering that section will create a directional reservation towards the dead end.
As long as that train did not reverse and depart at the last station, other trains cann follow up in the same direction and will for sure deadlock that system.
This is also what I would expect due to how directional reservations are working but this does not allow for replacing token block at those tracks.

Also, it should be mentioned that bidirectional track circuit blocks should be places before the first sation in the single tracked section. If you place it at the first station tile, it will sometimes deadlock.
I always place single direction signals as station exit signals in such single tracked blocks and use a bi directional signal at the first single tracked tile or, if there is already a station, at the last double tracked tile.
This seems to be working well.

Yeye that computer story