They do have handrails, and a nice grippy surface on the treads. Anda watches to make sure Rosy doesn't have problems and adapts to whatever pace R wants to go at but doesn't attempt physical contact unless R starts actively falling down the stairs.

When they get to the paygates at the bottom A beeps A's paycard on two different gates to pay for them both. (The first one activates A's yearly pass; the second one gets seamlessly detected as presumably for a second person and charged separately as a single ride ticket.)

Rosy emits a probable thank-you in R's mysterious untranslatable language and ventures through the gate! R seems unfamiliar with this exact style of paygate (slightly hesitant about the details of how to pass through) but familiar with the general concept (appears confident and oriented about other aspects of the situation, realized Anda was paying for R and made Probable Gratitude Noises).

"Did you come here from a different city recently?" Anda asks once they're through.

The platform has benches; Anda doesn't take one because Rosy obviously shouldn't sit down without pants and given that it feels politer to stay standing. The LED signboard above the platform says Inbound: 10m.

Rosy finds a wall to lean against, and glances at the sign in what seems like a plausibly literate way, and considers how to answer Anda's question, and settles on a weary nod accompanied by some more ironic laughter.

"Do you understand--I'm not expecting you to try to explain it in gestures or anything, but do you have an explanation for what that odd not-explosion was, about a minute before you woke up?" Anda still has no idea what happened there and A'd feel a lot better if someone did.

(The signboard decrements from 10 to 7.)

For some reason, Rosy seems to be having some trouble answering that question. R eventually settles, after a few false starts, on a deliberately ambiguous half-nod half-shake headwobble, plus a bonus handwobble to inject some extra uncertainty.

Unfortunate, but at least it's not a straight no. "Uh, in case you're disoriented enough to want me to say, this is Bridgecity's farstation. And I don't know how long you were unconscious; I heard a boom and saw a flash and looked over and there you were. You woke up pretty quickly so I've been guessing that the boom knocked you out but I didn't see that directly."

Oh look, it's our good friend Ironic Laughter, back again for another quick visit!

Anda cannot tell if that was a "you are saying obvious stuff and it's annoying" laugh or an "I am confused about something that isn't any of that" laugh. "Is there something else you're hoping I'll explain?"

Slow, uncertain nod that maybe started out intending to be a headshake.

"Okay. Unfortunately I'm not immediately guessing what it is . . . " A can provide the current date and time, and attempt to bring up a map of where they are relative to Bridgecity proper, though the latter takes a long time because they're underground and A's handcomp signal is trash.

Gestures possibly intended to request even more map expansion to higher layers?

A can zoom out the map . . . actually A can just give Rosy the handcomp and let R look at whatever geography thing R wants to look at. And peer curiously over R's shoulder unless R indicates an objection.

Rosy seems to be going for: all of the geography. All of it. Starting with the continents and working R's way back down toward Bridgecity, but also spot-checking some other seemingly random locations. Anda is welcome to shoulder-surf this expedition.

That makes Anda somewhat more concerned about Rosy's level of being hit on the head, but R already declined medical attention and maybe R just likes maps. A'll just let R look at maps until the train arrives if that's what R wants to do.

Apparently Rosy does want to do that! After the initial Bridgecity deep dive and some bopping around the globe examining various areas at various zoom levels in search of unknown features, R zeroes in on an area north of the Great Lakes and spends the rest of the wait studying it in detail.

Anda has a bunch of yes-or-no questions and isn't sure which ones to prioritize. A gets Rosy's attention when the train arrives if R doesn't notice; the PA system (which has been silent this whole time) additionally says "Inbound train. Inbound train." As they're boarding, A takes advantage of the interruption to ask "Where were you before you came to Bridgecity?"

...headshake. Also offering Anda A's handcomp back in case A wants it.

Perfectly reasonable thing to not want to disclose. A takes A's handcomp back and pockets it and leans against a wall of the (currently empty except for them) train car. "We need to go all the way to Interchange and get on the blue line." There's a map with the stop names on each wall of the car; the little LED next to "Farstation" is currently illuminated.

"Departing." says the ceiling speaker. The train, when it accelerates out of the station a second later, does not fuck around about it. 

Rosy is not quite sufficiently well braced to weather such abrupt acceleration, but has good reflexes and recovers without falling.

"Did the map answer your question alright? . . . Can you read Convergentlanguage right now as well as understand it?"

A hesitant nod and then a much firmer one.

"Do you want to try typing in Convergentlanguage and see if that works? That might be stupid, I'm not a neuroscientist."

Rosy considers that possibility for a few seconds and then nods.

Handcomp with the documents app pulled up. And opened to a random soup recipe in case having a sample of Convergentlanguage text visible helps.