Practical or not, I think the first jurisdictions to permit robot drivers will limit where they are permitted[1]. This would work well for that, though realistically, I think an online map of allowed regions and a GPS will be the real solution unless regular drivers want to be informed that others are robot driven, then it will be road side signs.

EOM

[1] I drove south through Nevada at 70+mph on a ruler straight road for 90 minutes without encountering another vehicle, human, or cow. Start there, expand as experience with the systems is gained.