Originally Posted by Pickles
Correct. I rode that one 4 years ago, and the new trainsets can now do 320-330 in that same stretch, although I'm not sure that is been included in the schedule yet.
The fastest operational trains in Japan are the 500 series, of which only 16 sets exist. I don't think they go above 300kph on the Sanyo line (Shin-Osaka to Hakata) or 270kph on the Tokaido line (Shin-Osaka to Tokyo).
Supposedly wind/tunnel noise is a big problem at higher speeds. Also, at these speeds, an additional 10% top speed isn't too helpful in reducing trip times. What would be great is better accelleration (I think this is where maglevs excel. Sorry).
http://www.h2.dion.ne.jp/~dajf/byunbyun/index.htm