What do you call it when...

sog

I am driving along and the trip is beginning to seem like I am in Twilight Zone. I begin to think I really am in Twilight Zone and then I arrive in a town (densly populated) and none of the intersections have street signs and the people there seem to be going about with no purpose. It got so intense I decided to stop thinking I am in Twilight Zone and got the hell out of that town asap and things got back to normal (whatever that is). WHEW

No I don't take illegal drugs. Later I remembered the song by U2: Where the streets have no name. Perhaps that is how they were inspired to write the song. (or did it inspire me to think I was in a town with streets that have no name). I wasn't listening to rock on that trip though.

Math Is Hard

Without knowing more, it sounds like you had a brief dissociative experience. Specifically, it sounds like an episode of "derealization" or "depersonalization" in that the environment around you took on an unreal, dreamlike, "Twilight Zone" sort of feeling.
http://en.wikipedia.org/wiki/Depersonalization
Dissociative experiences are often associated with severe traumatic events but need not be. Everyone has mild dissociative experiences from time to time, such as when we're daydreaming or watching a movie, and of course, they are perfectly normal. For other people these episodes are more intense and more frequent, and may be symptoms of another disorder.
Anyway, it doesn't sound like it's anything you need to worry about if you're not having these episodes on a regular basis.