a cool side-effect of building a bunch of trains instead of cars would be that it's a LOT easier to switch a hundred thousand trains to a newer model that's more energy efficient and green than it is to switch TWO BILLION CARS
not to derail my own post but I googled "how many trains are there?" and apparently the answer is 2.4
also "no to derail" wasn't intended as a pun
I used to have hundreds of trains, now I only have 2, France took the .4 ):