High-speed rail requires a new railway that has no grade crossings of highways, has wider-radius curves than freight lines, can have higher grades than freight lines, and has better rails and sleepers.<p>There is no chance of getting new high-speed railways built through the outskirts of major metro areas, so there will always be long end sections operating at less than 90 mph.<p>Smaller cities along the lines will also want service, so trains will have to decelerate, loiter, and accelerate multiple times between major metro areas.<p>The end result is that in the US high-speed rail is impossible to build, and it would operate on average at far less than the maximum speed.<p>Acela on the Northeast Corridor is about as fast as it will get. Even there, Boston to NY times could be improved by realigning some tracks in eastern CT and RI to remove tight curves, but even that has not been done.