Was playing around with surf when i came across this. Not sure if anyone else has seen it. You can actually go to other stations from here but you can't come back because it's ???  Does this mean that there are other ??? stations in game that just need to be found. If so, kudos to the dev cus i was pretty excited when i saw this

Not yet, but there will be eventually! The Sludge Wastes station is just a proof of concept for that mechanic.

In the finished game you'll have to discover every subway station on foot before fast traveling through them.