If it burned natural gas it probably wouldn’t even be that polluting and it would rock hard.
I suspect the actual technology within the tube was never Musk's initial concern. Similar to his other industrial endeavors, I think the calculus with Hyperloop had more to do with the economics of being able to manufacture pylons and tube segments offsite for quick assembly onsite, leveraging factory production and avoiding as much as possible site-specific costs such as land grading. And presumably he had in mind repurposing SpaceX technology for welding rocket bodies. Given a cost-effective way to build and put these tubes into place, and some ballpark figures on their characteristics--e.g. how much of a pressure difference they could reliably keep without inflating production costs--figuring out how to actually use them was just an engineering problem, which he then took a first crack at to satisfy himself the overall concept might be feasible.
So you have self driving cars, which will probably improve traffic flow, but it's fundamentally limited by geometry. If people takes more car trips, this will reverse some if not all the benefit of self driving cars.
Acela takes 3h44m from Boston to New York. Not much faster than the scheduled buses (4h15m) and comparable to driving the distance in your own car (3h55m if you stick to the speed limits)
I'd much rather take rail relative to the alternatives even if it takes longer and maybe costs more (especially leaving aside parking). And many others do as well even if it would be faster to drive.
And generally Manhattan is pretty walkable once you're there.
York to London is 215m and 2 hours, along a line that’s nearly 200 years old. Paris ti Lyon is 290 miles and takes 2 hours on a 40 year old track.
[1] https://www.sncf-connect.com/app/en-en/home/shop/results/out...
Those things are true, but like, jeez, the price. I for one don't even mind Amtrak's slow speed on its own, but not when it's more expensive than faster options!