[DeeMersey]

If you want to see an example of severely dipping track, I'd suggest a visit to Warrington Bank Quay.

Where northbound trains meet the bridge over the Arpley-Ditton line (this is under the platforms and runs somewhat diagonally, so you'll have to look carefully to see it until a train goes over) the track always used to drop by what looked like several inches, especially when fast freight went over at speed.

On several occasions I was convinced something would derail, yet regular drivers who must be aware of it make no effort to slow for it, so I'm assuming its considered to be within safe parameters.

DeeMersey.