How does one get ride of loud train-like noise when braking a 2002 Deville after a long ride (especially in stop and go traffic)?

"Train ~Like" ? Such as a train brake squeal metal on metal? It does not matter about being after a long ride, if you hear a metal on metal type sound it may be your device that has a tab that intentionally makes that sound to warn you your brake pads are thin and in need of replacement. OR your pads are already worn to the rivets and the squeal is that rubbing on the rotor. In either case your brakes are in need of inspection asap.

David - Thanks for your feedback but as noted the pads and rotors were changed and all passed MD inspection. Another 2002 Deville owner told me of the same problem (a train or truck horn not a squeal sound) when braking after the car has driven a while. The Cadillac dealership could not find the problem after changing rotors and pads. ...Ira