Train Length Lookahead Signal

[FuryoftheStars]

Set your interface preference for train visualization length, then use the white outlines to tell you exactly how far from the exit to place the second signal.

This ^^

Otherwise, the proposed addition of another entity just seems like bloat to me. The one imaged example of where it'd be useful seems to me like an early design concept that works great while the factory is small, but should be reworked as the factory grows and made more into the examples that ssilk then gave.

[BicycleEater]

Except this signal would allow mixed length trains to navigate a network efficiently, and in particular would allow networks which can support arbitrary length trains. At the minute, there is a huge penalty for mixing train lengths, as you have to signal for the longest train in an area. With this, you could signal for all the different lengths.
Another way of doing this would be to have a way of making a signal only visible for trains of a certain length (or trains of up to a certain length), which would give the same effect with more effort.
As is, its very easy to commit to a train length in the early mid game, and then want longer ore trains later, and either have to resignal or build two independant train networks.
Sure, you can say this adds game challenge, but I don't think it adds interesting game challenge.

[morsk]

I'll add that this is a unique Factorio problem because Factorio has no bridges/tunnels, and must use crossings that must be cleared by the full length of the train. Factorio copies its mechanics from OpenTTD, without the way you would solve this in OpenTTD, making us do weird things instead.

Like others here, I would like to use mixed-length trains. I like 8 wagons for ore, 8 or even 16 for build trains, but only 1 or 2 wagons for other things. edit: I now believe the "lookahead signal" is easier said than done, especially to make it performant. I would love a solution but I don't know if this is it.

[FuryoftheStars]

I do wonder if such a thing would require more UPS overhead than anything of now. Especially seems this means you're potentially having to look ahead through multiple intersections for longer trains. Additionally, because you have a mixed system, you run into the potential problem where the longer train has to wait for multiple intersections to clear before it can even start moving, but because the area is heavy with short train traffic, they keep zipping in and out of the various intersections, thereby locking the longer train in place for a longer period of time.