Hasn't even had time to get dusty.
In the early 80’s I rode Amtrak from Portland to Salt Lake City. Now, obviously it was almost all done by machines by then, but it was still bolted rail. (You can tell from on board the train by the “clickety clack” sounds. If you hear that, it’s bolted rail. Just a smooth swoosh? Welded rail.). We were doing 79 mph over a lot of it, and the ride was smooth as silk. It was on the Union Pacific and they did a fine job of track maintenance!It's pretty amazing to look at some of the trackwork from the pre-WWII days, when just about every bit of the work was done by large crews of men, working as a team, to shift the track into position. It was not uncommon for trains to run close to, or above the century mark back then!