620 MPH would be amazingly fast.
Currently China's bullet trains only manage about 250 MPH peak, although they are working on a maglev design that would allow a max of 600 KmPH (372 MPH). Their test trains already reach 311 MPH.
Of course, one difference is that the current bullet train service in China already carries people, not just packages, and already connects all the major cities in China.
China's 10 Fastest Trains — World Records and Benefits for Yo