That would be a lot more land devoted to freeways, and the associated maintenance cost. But beside that, the bottle necks are mostly not the number of highways, but rather the number of exits near the urban center. I'm skeptical that the roads in the urban center can scale much beyond what we already see in the most car oriented commuter cities in any roughly 2d configuration.
> That would be a lot more land devoted to freeways, and the associated maintenance cost.
The benefits more than make up for those costs, ensuring those who benefit also contribute to upkeep is a delicate balance but things like congestion pricing can go a long way.
Part of the solution is to have more freeways and thus spread exits more evenly across the city. Another part is to adjust city streets around those exits so they can accommodate a large influx of traffic. Similarly you optimize traffic flow inside the city by eliminating things that limit flow like street parking etc.
Going at least a little 3D is definitely required, but not necessarily big dig levels of 3D.
I don't think people living in cities want this, and so it's probably not going to happen. At least not in my city, which only has about two freeways, and people keep talking about tearing more of them down. I live half a mile away from one, and the noise pollution and tire dust pollution are both noticeable.
Maybe it's great from a suburban point of view still.
You don’t need to extend the freeway into the city for it to cut down commute times, removing street parking is one of the ways to then speed up flows within a city. Often you have a ring road around the city with people migrating for there, but such rings can have more spokes going out and often more bridges going in.
Alternatively, going underground removes the noise and dust assuming the city wants to pay for it.
