Advanced rail signal

[Epb7304]

TL;DR

A new type of rail signal that can change its behavior depending on the train that is looking at it

What?

Add a new type of rail signal that changes its behavior depending on the train that is looking at it. So that if a train is too long to fit in the block that the rail signal separates, then it will act like a chain signal, and if it can fit, then it will act like a rail signal

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It would also claim as many of these new signals as it needs at once (like what currently exists with chain signals)

Why?

This would allow for more complex and efficient rail networks to be much easier. Like if a network has multiple train sizes or simply a really long train size. This would make it very easy to straight up prevent deadlocks and players would not need to worry as much about ensuring that their largest train can completely clear an intersection by having a massive block directly after intersections, which hampers much smaller trains that need a fraction of the space.

This would not eliminate the need for normal rail signals or chain signals either. Chain signals would still be needed inside of intersections, and rail signals would still be useful inside of train stations. I imagine that this new type of signal would probably also be its own technology, like the selector combinator, and require higher level circuits, like red or even blue.

[alpedar]

I was thinking about something similar, but different.
Rail signal (or mode of signal), that would be impassable for trains that does not fit into next block (or not passing enable condition based on train length). This way they could guard rail sections designed for specific train lengths. And would combine nicely with OP's suggestions.

[mrvn]

A simpler solution would be for chain signals to claim as much space after the signal as the train is long. So if the rail signals after a chain signal are spaced too close together then the chain signal only goes green when enough of them are green to match the trains length.

No new signals needed, just smarter behavior.

Note: if there aren't enough rail signals after the chain signal to fit the train before it meets another chain signal then it recurses into the next chain signal.