That's the big one. What HSR needs is not even higher top speed but some control breakthrough that allows much higher train frequencies in order to cut down on stops via more trains that can serve more specialized connections (e.g. the local/through etc). No idea what that breakthrough might be, perhaps something as crazy as rocket-assisted emergency braking.
If you go from Shanghai to Suzhou via HSR a train goes roughly every 15 minutes. Most trains going east go through Suzhou (since it is a major hub) and it is roughly 30 minutes away which is a decent distance so worth stopping for. The train only gets to maximum speed for about 15 minutes in the middle.
Why not aero braking? You could install little flaps actuated with hydraulics along the train. This could probably be part of the normal braking system. The amount of drag produced by something like this at 1000kmh would likely be very substantial.
That's the big one. What HSR needs is not even higher top speed but some control breakthrough that allows much higher train frequencies in order to cut down on stops via more trains that can serve more specialized connections (e.g. the local/through etc). No idea what that breakthrough might be, perhaps something as crazy as rocket-assisted emergency braking.