Kay's Underground

History
Kay created the Underground initially, as means to visualize how the many personalities within her coexisted in her mind. It was with the help of Steve Dayton that she was able to organize it so it wasn't a complex web and she wasn't constantly shifting.

Originally, all the personalities had their own station. Steve helped her cluster similar personalities together. This condensation created the 8 stations, with each station representing one of her manifestations where Jane's appearance changes. Each manifestation can have different personas active in it.

Kay's "train of thought" is piloted by the identity known as Jeann Pepper, or "Driver 8", who goes from station to station, making scheduled stops. Whichever the most dominant persona on the train at any time is the one in control, and whichever station the dominant persona calls home determines the manife-station which Kay's body undergoes. Driver 8 isn't particularly dominant so she's almost never in control, except when the train is empty, but she can expel personas from a train if she needs to exert control. Because Steve insists that Jane Furness ("Crazy Jane") is the best combination of stability and dominance, Driver 8 keeps Jane riding the train more often than not.

But Jane when needs breaks or the occasional more dominant persona gets on the train... or if the Doom Patrol needs her to, Jane can have Driver 8 take her to a specific station where Jane can leave the train and get another persona to take a ride.

Of course, if things are truly scary and they need a hostile personality, like Jack Straw ("Daddy"), then that means Jane needs to stay behind in "Last Straw" and avoid or defend herself against the other hostile personas there while Driver 8 also has to keep the train running and at the same time preventing the hostile persona from taking control of the train (which would be bad).

Trivia

 * At least other two Doom Patrollers have been in the Underground: Steve Dayton and Cliff Steele.
 * When Cliff was between robot bodies and was just a brain floating in a jar, Steve took advantage of this detachment and had Cliff join him and Jane in the Underground to sort out a nasty situation.
 * Kay created the look of the Underground based on the network of train tunnels she saw on television growing up across the pond.
 * Sub-personalities within manifestations are close together within the system. For instance, Furness Road has at least three personas that reside there: "Jane", "Flit", and "Snow Queen".

Links and References

 * Appearances of Kay's Underground
 * Location Gallery: Kay's Underground