I was explaining the shape of traditional rail wheels.

BART's since adopted a very-slightly-beveled wheel design pictured here:

https://sf.streetsblog.org/wp-content/uploads/sites/3/2016/0...

Story:

https://sf.streetsblog.org/2016/04/07/new-bart-cars-show-age...

Note that that's as of 2016, six years ago.

The hunting phenomenon is real and has some interesting consequences. For freight trains, empty boxcars have a lower speed limit than fully-laden ones, as the hunting behaviour is greater with less weight.

High-speed rail systems required understanding and managing hunting action. Getting a case of the wobblies at 300 kph is an exciting but short ride.