> If every car on the road was synced then they could drive more closely to each other and at much faster speeds. This would optimize road space, decrease congestion, and reduce transit times.

That's not going to happen, not in our lifetimes. It's not safe to do this unless you have a critical mass of cars on the road capable of doing it. Given the average age of cars, it'll take ~10-15 years from such tech being mandatory in new cars to think about doing this. Being mandatory is of course itself over 10 years from it being available. And it's not available yet.

We're now a decade out from people starting to say "stop investing in public transportation because driverless cars will obsolete it," and so far driverless cars have only managed to provide a limited taxi service in a couple of cities, a far cry from deprecating public transit.

(Actually, I personally hew to the belief that driverless cars will make traffic worse, since it will probably increase the number of empty cars running around because traffic tends to be dominated by unidirectional bursts of traffic.)