What I sometimes wonder about is whether or not we'll some day seen these kind of personal pods configured for use on existing railway stock. Many times while waiting for a train, I've sat there pondering - "what if I could build some sort of portable segway-like thing that I could just clamp onto one of those rails on the track, step onto it, and propel myself down the line" .. and I honestly can't think of any major reasons why this wouldn't be viable in this day and age. Pods could clamp onto the existing rail, shuttle individuals around, communicate with each other to avoid collisions, and so on .. maybe I'm just not thinking it through well enough, but couldn't we just build better rail-transport devices at the personal level which utilize the existing infrastructure, instead of having to rebuild it all from scratch with incompatible systems?
Something like this, only better: