The large part of the complexity of implementing self-driving cars comes from the fact that the roadway is not a fully protected space. You can find a number of

The large part of the complexity of implementing self-driving cars comes from the fact that the roadway is not a fully protected space. You can find a number of examples of fully unattended automated vehicles that have been around for a while (for example, AGT people-movers that are common at airports), but they are dependent on a fully protected pathway so that they do not require very much intelligence. So what about roadways? Freeways have a certain degree of protection, but it's still not comparable with an elevated train ROW. It is certainly possible to develop roadways with a sufficient degree of protection for less sophisticated automation to be reliable, but it would be very expensive: they would need much more intensive maintenance, traffic density would have to be quite a bit more limited, they would need careful physical protection with at least fencing. In the end, I don't think that the infrastructure investment would be worth it considering that the period of time for which this infrastructure is needed will probably be quite short (in infrastructure terms).