The problem we have right now is that:
1. laying cables wouldn't work because there are a great many historic towns and cities (eg Amsterdam) and digging up cobble streets to lay cables for self-driving vehicles simple isn't going happen when those cities have so many bigger problems for autonomous cars such as trams, cycle paths, pedestrian zones and tourists what will just walk out in front of everyone in an unpredictable haze.
2. you have districts that are so under funded that the roads aren't even maintained in their current state.
3. So lets say you scape redeveloping the roads and have radio sensors on lap posts - then you have the problem that many rural areas in even richer countries like the UK don't even have street lamps. And what about countries like Australia and America that can have long stretches for tens or even hundreds of miles without a single house, let alone street lights to put sensors on.
I agree with you that normally this kind of problem requires a technical approach but the problem we have is that redeveloping our roads would be such a monumental overhaul that it would actually be a bigger job than developing the AI to handle our existing infrastructure. Plus redeveloping our roads only solves part of the problem - you still have the issue of other cars on the road, pedestrians, cyclists, unexpected hazards like fallen trees, etc. You could fix other vehicles on the road by allowing all vehicles to communicated with each other - like a mesh network - but then you have the problem of doing that securely (so you couldn't just "virtually ram" another car off the road by telling it there's an obstruction that doesn't exist) and you again have the problem that it would be more expensive and take longer to retrofit every single vehicle with that tech than it would be to write AI. And you still wouldn't have addressed the problem of kids, animals and fallen trees.
AI might seem like a naff workaround and maybe if / when we colonise a new planet then we might be able to build roads with sensors inside tubes that restrict access (I guess a little like an underground rail network) but for the time being AI is our best bet for autonomous vehicles.