schroedingershat

Roads always lose money, so that's still a win. Travel speed and coverage may be a limiting factor though.

Electric motors are now capable of >90% regen, so the braking energy argument against short stops doesn't work anymore (and the energy during motion strictly less than a rubber tired vehicle with a worse aspect ratio so long as the trip is no longer).

The amount of rail needed for short distance distribution networks could still be prohibitive in regions designed for road though. Even then one could still argue that the total infrastructure costs are lower by moving the destinations slightly given how much roads cost to maintain.

You'd have thought it was obvious, but everyone I've ever met IRL thought they'd be cheaper forever.

On the billions of acres no longer needed to grow animal feed for a small minority of global calories and protein.

You're trying to pretend meat isn't over and order of magnitude less efficient than other agriculture and it's just making you look foolish.

If the entire world turned vegan would it make a difference?

...yes. Plainly and obviously. Most land use would be gone overnight. Deforestation would stop immediately as would the second largest source of methane, one of the largest sources of NO2, and billions of tonnes of CO2 per year (about a quarter of all emissions). No other single initiative other than maybe ending urban driving would come close.

If you're in the global top 50% there is absolutely nothing stopping you from switching to a primarily plant based diet, and if you're in the bottom 50% you probably don't eat enough meat to be a major impact.

Sounds amazing and I hope one gets invented, but there is another solution as well:

You could make the wheels out of steel and run them on a narrow road also made of steel instead of oil byproducts, so they would wear out much slower, and any dust would be similar to naturally ocurring iron oxides (becoming relatively inert once it mixed with mud even if there was still some respiratory risk). It would be better suited to higher speeds and big loads and would compliment the other invention (maybe you could even put the small two wheeled car on the big steel wheeled car). Some kind of self-driving system would also be necessary to keep everyone safe