I'll echo that there are safety issues. Motorcyclists (I ride my much more fuel-efficient bike when I don't have something too big where I need my car), bicycles (which I also ride for leisure and errands close by), and pedestrians (same here) aren't going to work very well in that. You're not going to mandate that every person carry some kind of transponder and that it must always work. Where I live, many students are walking and cycling. I also think tractors, dump trunks, and other special equipment will still have human drivers for at least part of the journey for the foreseeable future.

Also, smacking into an animal at 160kph is terribly dangerous and potentially damaging. A blowout at that speed also has much scarier implications for control. A lot of hazards would need to have issues solved here as well.