Then why not state the actual point in the post instead of dancing around it with over-verbose descriptions?
Or: You could have just said "The rolling resistance of a rail car is less than that of even an empty semi-trailer."
Joking: That's because the Semi-trailer has a jack stand on it.
Believe me, if I missed the point (I didn't, actually, but easily could have.) several other people reading WILL miss it. (Go ahead, take inference from that, if you must.)
I actually did understand what you were saying though. Arguments and debates aside, it would take a substantial weight differential before metal rolling on metal would surpass rubber rolling on asphaltic concrete for rolling resistance.
Evidence of this fact comes when a simple trailer gets a flat tire, and the sidewalls are soft to begin with, such is the case (normally) with utility trailers (for lawn tractors). The trailer doesn't weigh more than 300 lbs, usually, and has two tires. One goes flat, it's just over 150 lbs on that one tire, *bias caused by yaw condition* yet you have to nearly exhaust yourself to get the trailer moving, whereas with fully inflated tires, you can move the whole 300 lbs and then some without a second breath.
Thinking in those terms, unless a rail car somehow managed to get a "flat" (see: locking up the brakes for some dummy drunk in his car, parked on the rails) it would continue to have less rolling resistance than even an unloaded 3-ton trailer (yeah, 6,000 lbs sounds right...)