[bombcar]

At some point even if your train is infinitely fast, you can't get above a certain average speed, dependent on the distance between stations.

Fun fact: technically the boring large Pacific Surfliner trains could be "high speed rail" since they could get to 120 MPH through Camp Pendleton if the line had PTC and was signaled correctly. As it is hits 80-90 through there, but it soon has to slow down for a stop.

To do high-speed rail right you basically need four tracks - a slower local service that stops at every stop, and a faster high-speed express service that only stops rarely.