What is the average life span of a railroad rail?

Answer 1

Interesting question, but like most questions, there is no simple answer.

On straight track a rail will still be usable when it is taken out.
Either because the requirements of the RR is for heavier guage rail or the line is closed down.
The year of manufacturer is cast on the web of rail, and I have seen rails in use that were built in the late 1800's.
On heavy curves, there are places where a rail is worn too much to be servicible in a few years, then they can do a "hi/lo" transfer exchanging the outside rail on a curve with the inside doubling the rail life.
It is the inside edge of the top part or "ball" of the rail that wears, from the friction of the wheel flanges on the inner wear surface.
A hi lo transfer puts the worn edge of the rail away from the wheel flanges and creates a new wear surface.

Answer 2

I would imagine it would depend on the amount of rail traffic passing over it, maintenance and the quality of the steel used in its manufacture. In a word, 7 - 10 years would be my guess.

Answer 3

Freight cars are retired at 50 years of age, by statute.