This brings to mind the curve at Folsom, NM on what was the load direction on BN's coal line.
There is a sharp horseshoe curve that went from wood, to concrete, to steel, to African hardwood
(like Ubinqua). The original wood wouldn't handle the load stress, the concrete wouldn't handle
the fore mentioned pumping from the load oscilations, the steel turned out to be too stiff and
now the hardwood (with drilled and essentially tapped "spikes") works just fine. It's also at
least three times as expensive as concrete. There's similar ties in the ex-WP Chillcoot tunnel in
NorCal. So after all this the coal now goes south thru La Junta and empties come back north over
the high dollar track.