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[tatans]

I remember seeing an article a long while back on the actual area that touches the rail on a 100 car freight train, the figure was preposterously small, so small it did not make sense, but upon thinking, a curved wheel on a curved track does not create much "footing"  Anyone remember, or happen to know the figures? ? ?   I'll keep looking.

[Deggesty]

This calculation is anything but precise, for the size of thumbs varies. I have seen that the area of contact between a wheel and a rail is about the same as the area of your thumbnail. So, calculate that tiny area, multiply by eight and then multiply by 100.

[petitnj]

This article reports a disk approximately 8-12 mm in diameter.

http://findarticles.com/p/articles/mi_m1215/is_/ai_90190965 .

Or roughly 1/3 inch in diameter. Because of hunting and slip that disk moves around the wheel and around the railhead. The idea is to keep the contact area about that size to minimize slip and wear.

Amazing isn't it?

And with 8 contact points per car each 10 mm in diameter we get 1/8 square inch per wheel or 1 square inch per car or a load of 100 tons per square inch on the rail.

[route_rock]

  About the size of a dime. so 100 x 8 so about 800 dollars worth of space ;)