Transit Dungeon Maps?

My wedding anniversary was this past Monday and one of the very cool gifts my wife to me (besides the green light to participate in game night on Monday*) was a book about mass transit maps, cleverly entitled Mass Transit Maps of the World.
New York City Subway Map
I have loved maps of all sorts since I was a child--I regularly created room-sized maps by taping together sheets of paper when staying with my grandparents (I was 6 or 7 years old...I didn't do it at home because of our dogs). I started working on a cartography specialization when I was an undergrad, but it required me to do a double major and I didn't complete all of the course work for the second major by time I graduated.
Istanbul Rail Transit Map
I am thinking that creating a transit map might be a groovy way to present the Montporte Dungeon, at least as it has been explored so far, to the players. As we are closing in on 50 sessions of play, it is hard to keep track of how the dungeon all fits together. I know the players seem to really struggle with this as they only see a small piece of the dungeon at any one time in Roll20.
Final Fantasy VII Transit Map
I am not sure how much work it would be to create a dungeon map as a transit map. I think the map creation would be the easier task. Figuring out the best way to graphically represent the dungeon and its connections might be brain-numbing.
Cardiac Transportation Routes
There is also the reality that a map that only represents to the players what has been explored so far becomes obsolete as soon as they begin mapping out new areas. The level of abstraction in a transit map might extend the useful life of the map, but at a certain point, the map would have to be modified or even completely recreated.
Sofia Public Transit Map
I am not sure how to represent the 3-D aspect of the dungeon. The Sofia Public Transit Map (above) gives enough of a 3-D perspective that it could be the basis for a good dungeon map. That would really challenge my rusty cartography skills.
Milky Way Transit Map
I might try to sketch out a rudimentary map and then see if I can create it on the computer (without investing too much time or any $$$ in software).
Springfield Transit Map