The buffers won't work for a roundabout indeed. The idea was for a simple crossing.Tallinu wrote:This is exactly what's done in most of the really high throughput junction designs. That concept was present even my old "Cross" design from before I had access to these great testing tools, and by now it's been pretty well refined, although there's certainly room for more innovation!mrvn wrote:I don't get your comment about multiple branches. In my suggestion each input would split right at the start into as many branches as there are outputs. Then you have buffer area for each. So the trains path gets decided before it enters the input buffer.
I'm not sure how well that idea would work in regards to a roundabout though, considering that they tend to put all traffic on the same circular path regardless of which exit a train is heading for. Having multiple paths onto the roundabout per entrance would be functionally equivalent to a stacker, as in an input buffer with multiple parking slots side by side, and all trains waiting at that entrance would be trying to use, or at least start out using, the same path through the roundabout. There's no way to know which train is heading for which exit unless there's a one to one correspondence between input buffers and accessible output buffers, and if all of a given set of input buffers merge onto the same roundabout track, then that's not the case. I don't think it's possible to make something for which that's true and which also qualifies as a roundabout (and not just something that resembles a roundabout visually, but can't actually be traversed in a full circle).
On the other hand, the idea of having a really huge roundabout with circuitry to help a train merge into the gaps might work, although detecting a gap large enough for an entire train and its track reservation to fit in might be difficult, and I can tell you from experience that it's also difficult to get trains to travel at a consistent speed and reliably do what you want them to do, even with some serious circuitry. But if you want to, you're welcome to have a look at the merge managers on a few of the MultiCross blueprints I posted recently for some circuitry that you might be able to modify to always prioritize one lane (the main roundabout path) over another (the entrance), or at least for an example idea of how I handled some of that detection and lane control.
For a roundabout you need all trains on the ring to move at the same (and hopefully full) speed. If you have identical trains that should be possible. Then it is "just" a matter of getting trains up to speed between the input buffers and joining the rings and timing it so they join in the smallest gap possible. But change the fuel or add a fluid wagon and your timing will be screwed. So a very fragile setup. Or if your timing is off by even one tick the error will cascade and probably collaps the whole system into chaos.