I wonder how the physics of freight on a ship vs a train works.
Yes, the static coefficient of friction of train wheels would make it harder to run a longer train, but I see some awfully long freight trains with only one or two diesels at the front!
With such care, the rolling resistance is very low, but it takes a bit more power to start moving. Despite that, one strong person can push one rail car, usually starting with use of a pry bar.
A locomotive cannot actually move many rail cars from rest. That’s why there is slack between each car, and to start, the locomotive is first reversed to push the rail cars together, then moves forward, pulling a single car until the slack is taken up, which pulls the next one, and so on. That’s also why you see one locomotive pulling so many cars. If a train stops on an incline for some reason, it generally needs to reverse all the way down the incline and start again.
The static coefficient comes into play during braking and if the locomotive wheels slip under power. For that, sand is applied to increase friction.
I thought it was a drawback at first, but now that I've moved away I kind of miss it.
I suppose you'd have to factor in other issues in the "real" world, like managing inclines, curves, and starts/stops for traffic. Boats generally have fewer constraints on those fronts. Also, boats can increase their size in more than one dimension, which lets them increase size more geometrically and efficiently (trains can only get longer, and hits practical length limitations faster).