[grey-area]

but it is some incomprehensible black box of weights, I won't be getting in that car.

You don't understand the complex weighted probabilities in your doctor's head either, but you trust them to diagnose cancer (which incidentally machine learning is beating humans at). None of the algorithms in doctors' heads can be formally proved to work in all circumstances, nor can the code that runs medical equipment.

A full understanding of complex systems (machine or human controlled) is not possible today in many domains, that's why we measure results. If the data shows that self-driving cars are safer, we will switch. At present, that's what it shows.

As to special roads/markers, these would make the technology less effective at dealing with the unexpected (crash ahead, moose on road, cyclist in the lane etc), and many of the leading companies don't think they are necessary. I can see cars forming networks which report danger, or adding more sensors, but don't think our roads will have to change for self driving, which will be prevalent within the decade IMO without infrastructure changes.