Narrow vehicles are unstablea. A narrow vehicle capable of carrying 7 people would be ridiculously long, and impossible to park.

There have been several studies that more lanes tend to lead to more traffic, not less. Here's a wiki article about the phenomenon: https://en.wikipedia.org/wiki/Induced_demand

That really depends on what you mean by more traffic. I think there are very few examples of extra capacity increasing travel time.

As you point out, several studies have shown that over time, travel time converges to the same value, despite additional capacity.

However, I think it is important to note that more lanes means more people are still getting from point A to B.

That's the point. More traffic more throughput. Nobody's saying the user experience is going to improve.

Peak hours are always going to cause congestion.

Wrong. More lanes doesn't lead to more traffic unless there are way too few lanes in the first place. I know of plenty of places where adding more lanes would not add more demand - North Dakota is full of them for example.

The only problem is we can't afford to build enough lanes. There is a limit to how wide you can go, and up or down is vastly more expensive than at grade. We could do it if we wanted to spend the money - but most such places find that a better bus and (not or!) train network is a better investment.

That's not necessarily a bad thing by itself. It means more people get to go where they want to go. But of course that can cause some negative externalities.

Creating more throughput instead of a quicker route isn't the same as saying "more lanes do nothing." So maybe your new highway lanes didn't cure congestion, but they did help alleviate housing demand some by letting more people commute with the same (albeit bad) commute time.

Yes, exactly. They said they're focusing on more throughput.

> If we were designing the interstate system today, that's actually a fun thought experiment. What would we change? I would probably focus more on throughput -- cars can be half as wide and still seat tons of people, 5 lane highways today could easy be 8 lanes of narrower cars.

Why would you go narrower? That makes problems worse for trucks and other cargo conveyance; note that in general, newer highway standards tends to increase lane width, not decrease them compared to older standards.

(I guess you can see the same effect with railroads--the UK railroads have smaller loading gauges than newer networks like the US, Germany, or Sweden).

In this thought experiment, we'd be able to redesign the whole road infrastructure. I'd say mandating smaller cars would be a huge savings in general.

I'm now imagining higher power Renault Twizys everywhere