@vincent037 Hi Vincent, this (and most) US long-distance Amtrak trains are normally operated at 79 mph, but there are a few segments across the BNSF southern Transcon route which are equipped with ATS (Automatic Train Stop), thus enabling these same units to operate at 90 mph. The lead loco has an inductive appliance mounted to the lead bogie on the right side, which passes over fixtures mounted to the track ties every so often. If a train exceeds its authorized speed or violates a signal, the ATS system will make the train stop. It’s rather old technology, though, not like the new PTC being installed.
Here in France, corals train can roll up to 200 KMH