Can Aerial Drones Unsnarl Traffic?

"Transportation officials and researchers believe that the drones hold promise as a way to keep an eye on traffic, route trucks and fix stoplights... But a drone could track groups of cars as they turn, revealing the way traffic winds through a network of roads. It could measure the way vehicles line up at red lights, and how fast they travel between lights. It could count trucks at rest stops or cars at park-and-ride lots, all in one trip."