Hmm, I can kinda relate to the highway analogy, or at least I have a highway analogy of my own in relation to me. I am diagnosed with both ADHD (inattentive type) and DID, and I often wonder how they interplay with each other.
I use my own highway analogy in relation to the ADD symptoms in that I frequently switch tracks of separate thought-trains, unrelated to my DID. For me the interplay with DID occurs when when we are triggered into a switch by thought associations. I don't know if that happens with the typical DID population or not, maybe it's quite typical - I just don't know. But we have a lot of 'thought deletion' and 'thought intrusion' because of the random association of thoughts into areas that trigger a protective alter to take over. It's like trying to walk through a minefield at times... there is buried material to be avoided, and sometimes the rapidly switching thought-trains drive us right over the top of them.
I am sure I explained that very badly! Oh well, it is what it is.