In a post on Reddit, it seems that some users are starting to see Google Maps offer up subway station layouts which should make for easier navigation within these stations, as you can see in the screenshot above of the Osaka Station in Japan. It is unclear how widespread these changes are, but the posts on Reddit are suggesting that it is being applied to countries like Japan, and also in the US like in New York City.
However we expect that it should eventually be expanded to more countries around the world. This also seems to be applicable to both the mobile and desktop version of Google Maps, so you can do your research first before leaving your home which would be useful when traveling and you don’t have internet on the go while in a foreign country.
As it stands it seems that these layouts are relatively basic compared to the rest of Google Maps, but given that not all users are seeing this feature yet, we can only imagine that Google is still working on them and that in the future we should be able to expect a more detailed version.