> Building more capacity usually induces demand

Viewed from a different perspective: we have so little capacity that most journeys are never taken.

I agree that in general mass transit is much better than cars. But tunnels do remove many of the arguments against cars: pollution (both CO2 and tire abrasion) can be easily filtered, noise is blocked by solid rock, tunnels can be crossed without knowing they are there, they don't interfere with pedestrians, don't reduce building density, don't create artificial barriers. Cars are still incredibly dangerous, but Elon's sledges would solve even that. Cars still take up a lot or room both in transit and when parked, but most other disadvantages are reduced or eliminated by putting them in tunnels.

People will just start commuting to further away places like from barcelona to london: https://www.theguardian.com/cities/2015/aug/11/commuting-fro...

You can argue for an economical benefit, but it's very hard to argue that they are larger than the costs.

Elon's tunnels don't solve anything. His cars are so large that the amount of people a tunnel can move is small. We can add more tunnels, but it isn't cheap, and geometry means we can't add enough - there is only so much space below us and you need to keep tunnels apart.

> there is only so much space below us

Is this actually a practical limitation? You could go a mile deep, and pack the tunnels way more densely than roads on the surface (since we don't need to put buildings in between the roads).

> But tunnels do remove many of the arguments against cars: pollution (both CO2 and tire abrasion) can be easily filtered

I have never seen this done. Questions: How? And if it's so easy, why don't we do it?

Or maybe it’s not inducing demand but fulfilling demand. I don’t get this odd position often taken to attack cars. People like fast private point to point transport.

They are just addicted to it, but they don't like it

If they really liked it they will learn to drive well

We could also say that people like alcohol or drugs, but the truth is that it is addiction

That's why they are heavily regulated

> If they really liked it they will learn to drive well

I don't see how that follows.

I recently heard an economist make a point about induced demand which I found interesting.

While it's true that building more roads doesn't always reduce traffic, the bit that most people miss is that even if induced demand fills up the new capacity, in the new equilibrium more people are able to use the road, so there's more utility being gained.

Put another way, at the margin there's a lot of latent demand that is unfilled. If you were to keep building roads, then at some point you'd meet all of that latent demand and traffic would go down. The fact that increasing supply also increases demand is not necessarily an argument against building more capacity; you could actually use it as an argument _for_ building a lot more roads.

(Of course, without dynamic pricing it's really hard to figure out whether it's actually worth building more capacity; you could build a new road at a shared cost of $100 per new driver per month, when they would only choose pay up to $10 per month to drive instead of do what they did before. Dynamic pricing models tend to be unpopular though, particularly as they can be construed as a regressive tax-like burden.)

Yes, but if it's a car that's bad. Cars are not as efficient as shared transit. https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/Pub...