"Do you know where the subway is?"
Translation:Wiesz gdzie jest metro?
In British English this would mean przejscie podziemne, rather than metro.
a passage under a road or railway for people to walk through
znać - to know X (to be familiar with)
wiedzieć - to know, that X; to know about X, etc. (to have the knowledge about something). So also here.
There's no such thing as "British" English: Scottish, English, Irish and Welsh usages are very often different, and there are differences within each country too. The underground railway in Glasgow is regularly called the subway.