In theory it could reduce the number of cars required for a population, but not traffic. Whoever is throwing this stuff out there seems to forget that cars spend most of their time parked, not on the road. If there are fewer cars, but those cars spend a significantly higher percentage of time driving, traffic will be the same.

Uber may actually make it worse, as there are people trying to go places, and drivers simply driving around waiting to get a fare, and then driving to get them (a new leg of the trip that didn’t exist before).