Signal not switching to yellow/green between 2 fast trains

[aka13]

Hello everyone,

I am not sure if this is intended behaviour, so I decided to make sure.
I am running a train counter based on a simple contraption, which pulses once, when the signal in a block switches from red to yellow/green.

I assumed that such a contraption reliably counts all passing trains, since a signal must(?) turn yellow for a tick, when two fast trains are going one after another.

I have found the opposite to be the case. If two trains follow eachother very quickly, one of the signals into the block stays red, while another, as expected, turns yellow between trains.
I have attached the save and the situation in question to this post.

Signals.png (1.79 MiB) Viewed 1241 times

I have of course tried to run the thing without mods, and got the same behaviour. I assume, that only one signal into the block can turn yellow then, and I have to use the upper signal as the detector, and such a "sideway" detector is therefore unreliable?
I would appreciate an insight, this project is slowly sucking the life out of me.


Oh boy, sorry, seems I got the wrong forum for my question. I would appreciate if it could be moved to gameplay insted of technical.

[SupplyDepoo]

Only the rail signals that a train is pathing through will turn yellow. Other signals pointing into the same block will always be red. So yes, you have to read the upper signal instead.

[Zanthra]

The requirement for a signal to turn yellow is not just that the train has pathed through it, but also that the train does not have enough stopping power to stop before passing through it. The signal will turn yellow, and all other signals into the block will turn red to prevent them from conflicting with that train.

It's reasonable to assume that a block can be freed by one train and claimed by another (one that is either already stopped or slowing down to stop waiting for a red signal into that block to turn green) in the same tick, meaning any other train signals into that block remain red.

[aka13]

Yeah, it totally makes sense, I reread the wiki more carefully, after your comments, and it all makes sense now. I have switched to "on-rail" sensors everywhere where I need to count trains.

Thank you guys.