I read this in the (1947) article cited:
"Amtrak’s 150-mph (241-km/h) Acela creates its own bank angle by tilting up to 4.2 degrees. If the Acela is operating on a curve whose out-side rail is raised 2 inches (5 cm), the Acela can speed as if it is on a curve that is raised an additional 7 inches (17.8 cm) higher—for a total super-elevation of 9 inches (22.9 cm)."
And it would appear to do that without significantly changing the height of its center of gravity. In the context of this discussion of tipping forces, that's quite an accomplishment.