These days everyone is losing their shit over autonomous, or self-driving, cars. Research is being conducted, laws are being changed, and huge money is spent. In all that everyone seems to forgetting that sometimes the simplest solutions are the best solutions.
Sometime in the 1960’s, as per the above randomly found YouTube video, Citroen has developed a self-driving car. Or at least a “automated steering” car. Kind of. In those pre-digital, pre-GPS, days, the Citroen DS was modified with magnetic sensors to follow the cables buried under the asphalt. While not quite self-driving, it clearly worked.
Implementation of a modern version of a magnetic system like this is possible, if needed, but the costs would probably be astronomical. Addition of speed-control systems to it would be easy and basically already exists. The biggest advantage of this system could be that it could work in conjunction with, or as a redundant backup to, the modern satellite or cellphone tower based systems.