Which passenger route has the smoothest/roughest track?

Of all passenger lines in the US with regularly-scheduled service (i.e., commuter trains and Amtrak routes), which has the smoothest track? Which has the roughest? Which railroad (or host railroad) spends the most per mile on track upkeep, and which spends the least?

Thanks.

I would assume that recently laid passenger trains routes with no freight, or very little freight, would have the smoothest tracks. Therefore I would suggest DCTA "A-Train" and NCTD "Sprinter" tracks should be relatively smooth. But they only laid 110 lb rail vs typical 130+ lb rail on main line freight tracks, so they may not remain smoother long.

A great deal depends on the equipment you are riding. That said, I find the former Burlington route between Chicago and Denver to be quite rough but then it was a rough ride on the DZ pre Amtrak. Last year I rode on conventional lightweight (private ownership) between Chicago and Albany and was surprised at how rough that was. I guess for smooth track I would have to say the former Santa Fe main. Also, I was impressed with the reroute over the former CEI St. Louis - Chicago last year. Boring, but smooth.

I don't know much about this. But I do know a good indicator of smoothness of track is how round the pancakes turn out.

Les