Hmm, that would certainly be a solution. However, I'm a little dubious as to how this would work in practice. The current signage can be thrown on the back of a

Hmm, that would certainly be a solution. However, I'm a little dubious as to how this would work in practice. The current signage can be thrown on the back of a truck, bashed about, subjected to dirt and weather, and is really easy to use. Smart signage would (likely) be more fragile, (likely) require charging or similar infrastructure, and would require configuration -- so that the sign can communicate in which direction of travel it applies and so on. Certainly not impossible hurdles to overcome, but the costs associated seem very high -- in terms of manufacture, maintenance, and training. For what it's worth, I suspect that we will see FSD cars operating with infrastructure likely along the lines you outline in the not-terribly-distant future -- but I suspect that they will operate within very clearly prescribed zones, like freeways and highways.