Track-laying train

[Thanks to Kirk]

A train made for the automatic laying of train tracks. Real kewl.
... Look at the number of tasks these machines do. Thats a real engineering accomplishment.

Once in the middle of the night I saw a train which sucked up the fist-sized rocks which are between the train tracks, and spit down clean ones! The noise it made was absolutely fantastic, it was like an industrial art happening, I loved it. I lived then just fifty meters from the tracks, and this train was only a couple of meters behind a fence.
As to why those rocks would need replacing, beats me.