In answer to this picture's question:

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I originally said that it was a herder's shanty frame that was left there. But the walkway in between the rails doesn't make any sense when comparing it to a local picture of a herder's shanty:

click to view

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So my next suggestion is that at one time it was a shed for a MOW Speeder seen here:

(Credit: NARCOA)

These would be used to deliver parts or to repair small sections of the rail line without major work or machinery needed, and you could turn these things around (U-turn) in a matter of minutes so it won't tie up the line for the next freight train to come through.

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That's my best guess... Anyone is welcome to add to this conclusion.

-RailGuy88

It's definitely a classic "take off" for a rail motorcar, have parked on one myself hundreds of times.