Well you can't run your internet backbone at all unless you want to connect it to the internet. For something like a network of traffic light controllers, traff

Well you can't run your internet backbone at all unless you want to connect it to the internet. For something like a network of traffic light controllers, traffic sensors, variable speed signs, traffic monitoring cameras, ect... You either need to connect it to the internet, or some sort of incredible large intranet that would be distributed over such a large area as to only marginally reduce the attack surface. Unlike say a power plant, where all of the controllers, and all of the systems they are controlling can be contained within a single facility.