I can't see these working over here. On the US' grid systems? Sure. On British roads with sweeping side lanes, mini roundabouts, double mini roundabouts, 3-5 lane roundabouts? How the heck are they going to look right and know, during rush hour, when they've got time to get out without slowing the other person down? How are they going to look left and know that the movement there is ok, because it's expected and shouldn't affect you (but could)?
Swindon's "Magic Roundabout":
Roundabout at the Arc de triomphe, Paris
(actually, if we could replace all cars with self-driving cars, that would actually solve the problem there :p)
What about temporary traffic lights or rolling roadworks?
I love the idea. My commute feels like a big waste of time, imagine if I could be working in the car or just reading/relaxing. But I don't think we're going to see these on this side of the pond for a very long time, if ever.