I think you'd be surprised. Look at the difference in cost per passenger mile.
I guess you're comparing the total cost of trains vs a subset of costs of cars, as is usual. Road use and pollution are free externalities after all.
Source? The biggest source of environmental issues from EVs, tire wear from a heavier vehicle, absolutely applies to AVs. VC subsidizing low prices only to hike them later isn't exactly "without subsidy" - we pay for it either way
As soon as a mode of transport actually has to compete in a market for scarce & valuable land to operate on, trains and other forms of transit (publicly or privately owned) win every time.
Where trains work they are great. Where they don't, driverless electric cars seem like a great option.
Is there a magic road wand?