It would be actually interesting to hear about this difference from someone who is working on autonomous cars for both highways and Autobahns. I still wouldn't call the difference 'massive' (at least not in terms of how much the technology would need to advance). Overtaking and avoiding slows down is an issue on highways in other countries too and once it is implemented it could possibly be easily adapted to traffic moving at a faster pace. Being trapped on the right lane happens quite often, but you generally have this problem when the current lane is crowded. It's not a special case for the Autobahn. I agree that the speed difference can be much higher which would possibly require a ToF sensor with higher range than what is currently built into the Google cars (only about 200 m).