Even if every current vehicle was replaced by one of these I don't see how it helps congestion. Sure cars can drive slightly closer together but not enough to make a big difference. And unless every road has lane width reduced and new lanes created we won't get more cars abreast either.

The only things that will help is fewer journeys at peak times, and some sort of inter-car communication system that manages traffic flow far better than our slow awkward human brains.