Do the Japanese run Shinkansen lines at 100 miles or so? I like the idea, I just wonder if other countries would build such a thing for a relatively short route.
Well there is a Shinkansen of approximately that length (infact shorter, the
Nagano Shinkansen which is the first part of a long delayed project to build a longer one), and there were the long delayed plans to build one to the Narita Airport which have now been scrapped..
I do note that it would be of comparable length as HS2 Phase 1 and would probably require rather less tunnelling.
You might extend Crossrail and the residual inner suburban trains to Chelmsford and put the first stop there, and probably make extensive use of classic compatible trains so that everywhere off the Norwich-Ipswitch-Chelmsford-London corridor gets service over the new line, freeing huge amounts of capacity on the current line for freight.
A line of this length would likely have 4-5 Intermediate stations based upon the standards set by the
Tōkaidō Shinkansen.
If I was speccing a High Speed line for Norwich, I'd make use of the route I'd use for the East Coast one (via Cambridge) and branch towards Norwich after Cambridge.
Problem with Cambridge is that you then end up with a line that doesn't really relieve the existing lines and just shunts yet more trains into existing termini that might not be able to cope practically.
It also cuts down on your feasible stopping patterns in the name of improving capacity on the "core" section.
Shinkansen philosophy is almost the polar opposite of the HS2 Philosophy.