They are probably ways to improve existing roads for semi-automated vehicles without creating dedicated infrastructure (which is by itself, not possible anyway,

They are probably ways to improve existing roads for semi-automated vehicles without creating dedicated infrastructure (which is by itself, not possible anyway, it's kind of hard to create dedicated streets in a dense city for example). The roads could have captors/sensors/tags added gradually to them. For example, some near field devices planted in the road and broadcasting information such as the name of the road, mile mark, line number/side or traffic lights broadcasting if they are at red or yellow or green or signs such as Stops broadcasting their presence. This would help autonomous vehicles a lot (instead of having to scan the infrastructure and deduce the environment, the infrastructure will broadcast the environment, at least the static parts, directly), while at the same time not be that costly (compared to the initial cost of the road or even its maintenance costs).