Ok, so first off, there's just one car. There will be one segment for each person in the car, of varied topics - so 7 or 8 different conversational segments. Between each of the segments there'll be 'links', which range from simply watching the scenery, to chinese fire drills. Basically, most ideas that aren't conversational can be used as a link.
People can be in each other's segments, but the main character of the segment will be the focal point.
The only problem I really have with it anymore - and it's not a problem so much as an observation - is that, to me, if everything happens in the same car it's less about the universiality of road trips and more about this particular group of people. But I think I'm ok with that.
So yeah, I guess that's pretty much the same thing Andy said, I dunno why I didn't really get it before.
Also, on a completely unrelated note, I thought of a couple new things. From now on, if it's conversation, I'll call it a segment idea, and if it's action or just random, it's a link.
One person's segment is over CB radio with just some random person.
Getting pulled over is really short, just a siren and the Driver being like, "Fuck!"; Fade to black.
Someone shouts, "Look, a DEER! (or whatever, some animal)."
Flying a Kite