Roads don't scale well regardless of whether the cars are self-driving. Once you get enough cars on the same highway, there's an inflection point where speeds drop quickly. This only gets worse as you increase the radius of viable commuting distance, since that increases the total number of commuters.

They scale when designed with scale in mind.

Most cities need more limited access highways not just more lanes. Suburbs extend much further along highways for obvious reasons, yet they get built on the way to somewhere else not just for regional transportation.

A perfect example being the south east of DC getting extremely underdeveloped relative to the west. But you can see the same pattern around many US cities.

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.

DC had a rather powerful lobby that tried to prevent building highways, particularly inside the District's limits, so very little got built in the DC-controlled areas (like the southeast).

The west was in Virginia and didn't face nearly as much opposition. 50 years later, the economic growth has been concentrated in Virginia where adequate transportation facilities were built.

Exactly, massive economic growth follows such investments but people have largely stopped looking forward.

> A perfect example being the south east of DC getting extremely underdeveloped

Are you talking Belvior/Mason Neck or King George/Westmoreland/Northumberland counties? If it's the latter, a lack of development would be tied to the extra distance of working back up the peninsula. (I was born in the former)

It isn't 1950; people are mostly going places other than city centres. Old style rail doesn't work particularly well for that.

so you have high speed long distance and commuter rail, and then local transit options. and you can stop at places other than coty centres. my route from berlin to hamburg has a bunch of smaller stops.

asia and europe get by fine with rail. if china can build 20 subway systems and 50 HSR routes in 10 years so can america

Rail doesn’t need to be a 90% solution, even 10% makes a major difference on the margins.

Infrastructure like subway stations drive up local prices which means people who don’t use them tend to migrate somewhere else.

> It isn't 1950; people are mostly going places other than city centres.

We suburbanites avoid doing city stuff because the 11th-14th commutes (that week) would suck.

Lol talking about rails in the US is pointless at this point.

US uses quite a bit of rail, just not for long distance travel. DC metro for example has stations over 30 miles out, with other options extending that to over 60.

A big part of this is having unsubsidized parking, if you or your company is paying 20+$/day on top of driving the incentives change.

Freight trains are still a thing. About 20 years ago Buffet bought BNSF.

Thus the long distance travel caveat.

US Fright is doing ok, but it got heavily dependent on coal which is going away fast.

In US, number of miles of rails only ever goes down.

https://www.statista.com/statistics/183410/united-states-cla...

Removing redundancy is one way efficiency has gone up so much.

https://www.bts.gov/sites/bts.dot.gov/files/Figure1_5_0.gif