You do know that over half of area of the US has no wired Internet or POTS , right? Yeah, 90+% of the population is concentrated enough to get access to wires. It is a lot of land without decent communication infrastructure.
Laying fiber alongside all the highways and streets isn't a bad idea, though.
I mean, it should be easy to determine the difference in local vibrations between "no traffic," "normal traffic," and "a bunch of people sitting in one place with engines idling." That could pinpoint the location of traffic jams and accidents on a continuous basis. Local emergency services could be notified of at least some accidents automatically, without waiting on someone to report them. The same thing goes for mobile map apps routing around traffic jams.
Even better, the info could be used to adjust timing and synchronization of traffic signals depending on how heavy traffic is, so you don't back traffic up as much during rush hour, but you don't have to wait forever to cross the main streets during off-peak traffic.
