It'll be really interesting to see how driverless cars negotiate things like natural merges (a freeway losing a lane), and how that affects traffic flow. Ostensibly they'll be as efficient as possible, but if two lanes become one, there's going to be some slowing regardless. Furthermore, in a vehicle that also ostensibly wants to get you to your point of interest in as timely a manner as possible, how does it decide whether to subject itself to staying in a right lane where it might be subject to moreane merges, or does it ever decide to go around a particularly bad or congested spot for the sake of getting you to the destination?