They're beating us in this one.
Current traffic monitoring systems use either CC video analysis, ramp meters, magnetic loop, or blue tooth detection. I've heard of systems to pick up tire pressure indicator signals also, but I haven't seen them first hand.
With all of that, we get ~5-7% of the vehicle speed data on select routes.
In 2017 new requirements go into effect to require all vehicles produced for use in the US to include V2V communications systems. Most of these systems also include V2I communications. Even if they don't, I'd expect detecting that a specific V2V entity just drove past is going to be trivial.
So by the end of 2017, we're going to be on parity with all of our current assorted solutions for penetration. By the end of 2018, we'll have double the penetration. By 2020, roughly 20-25% of all vehicles will contain V2V and/or V2I communications.
So what does that mean? It means we could generate optimum route data and re-route traffic based on travel time recommendations before they get onto a major road with limited access and a traffic issue on the desired route.
It also means we can identify true bottlenecks and take completely new approaches to road engineering and project prioritization. This alone is a multi-billion dollar a year industry, funded largely by tax payers. If we can find more efficient ways of taking on these projects, it means less expenditures (or more projects).
But it comes with down sides. A policing agency could in theory query the system to see where you currently are, or where your vehicle was at a specific time. It also makes it possible for the mile traveled road tax, where you can be taxed by mile driven, and those taxes can vary and be distributed by municipalities that own those roads. And of course there is a security concern that a hacker or malicious user could determine your driving habits and use the information to their advantage. I did even hear a member of the law enforcement community asking about such a system's ability to disable vehicles remotely in the case of excessive speed, chases, etc...
Basically, there's a huge shift coming in the US and how we (and the government) interact with our vehicles.