[stcredzero]

Have you thought this out? What happens when someone hacks their own beacons for lulz? So then the beacons have to have public key cryptography. Now all of the firmware will need to be audited and kept updated. Will there be over the air updates? What if someone cracks or steals the key? It seems to me that a target as juicy as "getting control of the North American road network" would be worth a major national power throwing a significant fraction of its resources at it, so that inflates the computing power such devices will need.

[MOil]

What if someone would install their own traffic light right now?

[stcredzero]

That's immediately visible to people with eyeballs. The first sign that something is going wrong isn't going to be a car colliding with another car. It's going to be, "Hey, why are those kids installing a light with a step ladder?"

Have you seen a traffic light? They're pretty substantial. How long would it take for you to make one in a hackerspace?

Contrast this with hacking OTA updates for traffic beacons. You might not even have to change any atoms around to do your dirty deed. You might not even have to be there physically.

[samstave]

Why would it need all that if the only thing it's doing is simply announcing its state?