We note that there is some trend, however minuscule, toward smaller cars. Ones that fit two to a parking spot. Some places have more of them than others.
There are even ideas to put two to a lane.
Now, even the god Google is in the fray with cars that look to be able to drive themselves. In this way cars can bunch closer together.
Each of these improvements will make the private automobile more useful, less polluting, more desirable, more ubiquitous and our roads more congested.Pollution-free, convoys, two to a lane. More. But roads cannot be supplied effectively as fast as we can populate our fleets. This is so because of space, politics, money, and environment.
Space, not automotive innovation is the limitation; there is no lack of automotive innovation. But we do lack the courage to manage demand.
The market makes cars better by satisfying demand. The market could make mobility better by managing demand with time-distance-place pricing.