Freight railroads reinvent the wheel.

[Binkie The Clown]

2. It blew my mind when I first found out...

... That the profile of the wheel and of the rail itself act together to cause the wheel to ride up to a higher diameter section on the outside rail of a curve, thus acting the same way that a car's rear end differential gear works. In other words, the inside wheel and outside wheel are solidly fixed together, yet when going around a curve, the outside wheel, turning at the same RPM as the inside wheel presents a larger circumference to the rail top, and thus travels a longer distance than the inside wheel.