Why crowning is provided on head portion of any rail crosssection?

Question

Why crowning is provided on head portion of any rail crosssection?

Answer 1

so the rail don't wear as quick, we change 'em all the time

Answer 2

To reduse the air resistance(It is a airodynamic shape.)

Answer 3

I dont know the exxact answer but what neel told is absolutely wrong, sicne aerodynamic shapes are provided only for non stationary objects (not like stationary objects like railway tracks) to reduce the drag force and therey by reducing the power reqruied to propel it.

I will give it a try.  To reduce the friction between the wheels and the track since there is only a line contact between the track and the wheels.