Factorio Forums

When you upgrade the entrance or the exit to an underground belt, the other node should be upgraded as well. An upgrade of a complete belt, should also require two nodes, making "half" upgrades of an underground belt impossible.

Right now you can upgrade either the entrance or the exit to an underground belt. I don't get how that would even work, since I was assuming that the speed of the underground belt was indicated by the entrance AND the exit, so if the entrance is normal, and the exit is fast, does it speed up along the way?

In general yes, but that would simply be annoying if you make nifty things like viewtopic.php?f=18&t=3211&p=23636#p23636
or bringing up to three underground belts into one tile like viewtopic.php?f=5&t=4596

See https://wiki.factorio.com/index.php?tit ... ound_belts

So it must be only an option.

Edit: There is a mod: viewtopic.php?f=92&t=20071 {UBS} - Underground Belt Spotter