Right. So when the subway gets crowded, the ideal thing to do is reduce the number of trains per hour so that people stop trying to ride it.

That's like saying, "we shouldn't build more hospitals, because we don't want to make more sick patients". It's only "true" if you grossly botch your before and after counts.

But you are ignoring the human and economic benefits of increased travel.

A better example would be someone pulling their belt so tight they can barely move, and then letting it out.

But we let the belt out all that way, and the belt still touches their waist!

Then there is more demand. Keep going. There is nothing that has unlimited demand.

You can't reduce demand by constraining supply, all you are doing is making people unhappy.

If your policies are very free, you'll find people will figure out how make things more efficient. For example inexpensive delivery will become possible if there was enough space for traffic.

I know this because I've lived in dense cities (no delivery service - it's simply too hard to find parking, and thus too expensive) and wide urban areas (every store offers delivery because it's cheap and easy).

And that's exactly the opposite of what everyone thinks will happen - they want cars off the road, and replaced with delivery, without actually making delivery practical (i.e. inexpensive).