Recently, I've been traveling more than 4k km by car, and I had some time to think about stuff not connected with gamedev. In Germany I've noticed a strange sign - speed limit depending on slipperiness of the road surface. It was strange, because there were no precautions if weather is ok, so you can go 300km/h if your car can, and in case of rain you can go only 80km/h, so it's quite discrete. And than the idea came - why not measure the state of the road and show the speed limit in electronic form. For example in dense rain - 80km/h, in snow - 50km/h, in light rain - 120km/h and so on. We kept going, and on the bridge there was a sign - in case of wind, 100km/h or something like this. The idea is even better here - just measure wind speed and show appropriate limits. The method is great because the sign can measure a lot of parameters at a time, and using some heuristics it can show the speed limit, or some other information. What other info? For example - imagine a sign showing a pedestrian crossing. If you go at night you usually can't see anything, so slowing down is the only option, but even going 50km/h is too much if someone enters the crossing. The solution is simple - show some additional info, that there is someone near the crossing, so that the driver knows that he has to stop, not only slow down. It's not easy to implement, but in my opinion it's not impossible. Smart signs can also take into consideration some other stuff, like traffic - read this. In my opinion, the method has almost no limits, and would really improve safety on roads. The only question is, will politics spend money on our safety? I don't think so, they need money for PR :)
Let's go further - the speed limit also depends on the car, for example big truck should have much bigger limits. Why not implement traffic signs... in cars? Imagine a display that shows you the limit, or in extreme it can even automatically limit your speed. The idea can be really simple - all traffic signs have some transmitters attached, that broadcast restrictions at some place (some norm would be required). Receivers collect those broadcast, and analyze them, for example taking into consideration mass of the car, state of it's tires and so on. But for now this is rather science fiction, because all cars would have to implement this. Maybe it's a good moment to start such revolution, this depends on motorization brands. Remember, that such a solution doesn't have to mean that we remove all "classic" signs - they can stay, we can just add some new features to them.