> I do wonder, though, if you might be causing too much outside rail wear, or possibly
> needing some kind of better fastening, by operating much faster than is traditional?

Indeed yes, that can happen. Especially with older methods fastening rail to wooden ties. But it is much less likely with modern fasteners and concrete ties - assuming they are constructed properly - that is; and mounted on sufficiently resilient roadbed. Still, it will always be something that must be accounted for.

I have seen a few cases where even moderate speeds caused similar overloading on the outer rail and its fasteners. Oddly enough, the worst was where there was an extremely super-elevated curve (more than 8 inches), mounted on a very rigid concrete slab in a transit subway. Too much actually! And also bolted on a too hard non-resilient surface! Speeds had to actually be lowered to below equilibrium, before the excessive track wear stopped.

We recommended that short of actually replacing the concrete slab with a more resilient and softer roadbed; that they remove some of the super-elevation, and then operate at 3 inches cant deficiency. Being much below equilibrium can also be very uncomfortable as well. They declined that advice and are still operating well below equilibrium, causing excessive wear on the inside rail and causing lots of extra noise in the tunnel. And they wonder why passengers are uncomfortable and constantly complaining -- but alas, we got paid anyway! So apparently, there is a practical limit to super-elevation; especially on very hard roadbed. That would also apply to track where trains of widely different speeds operate.

In another case, Thousands of Amtrak's concrete ties on the Northeast corridor, were not properly formed during manufacture. Thus for many years now, a lower than intended speed limit has been imposed in many areas south of NYC. Projects to fix that are just now being completed. Hence the renewed interest and recent Acela tests of up to 156mph (250kmh) in those stretches.