Train accident

Strange sound is sometimes heard when the train goes on curvature way. The frequency of the sound is over 1kHz and uncomfortable to be continued. The reason of this kind of strange sound is the lack of physical mechanisms on one piece wheel, necessary differencial gears are not equipped like automobile. And the fact has much to do with derailment run aground occurred before, though the report of the cause had been some composite reasons by Accident Investigation Board.
As for my opinion, the applications of the differential gear system is necessary on adequate wheel portions instead of long running solid one piece combined wheel, becasue many an accident had been triggered by this fundamental physical reason, strange pendulum constructions may invited but after that, the first is human's life safety, no?