I think the burden of proof is on you here. It seems like such an unlikely claim as to be outlandish. I'd max out such a claim at 5x (assuming that each car has 4 useless passengers), which is obviously extreme already. 10x seems ludicrous.
I'd go even further and say that vehicle miles are more valuable than train miles because vehicle miles generally head exactly where you want to go without detours, without time-consuming stops and without a fixed schedule. A fairly direct line of travel, no unnecessary stops and ability to depart at any time make vehicle miles much more valuable.
For some very very specific routes, train miles may be more valuable, but generally speaking they are less valuable.
