What do you consider "high speed"?
Taking a look at Amtrak's schedules and do some basic math. Here's the Acela average speeds between stations as published at:
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Boston South to Boston Back Bay = 6 minutes over 1 mile = 10 mph
Boston Back Bay to Route 128 = 10 minutes over 10 miles = 60 mph
Route 128 to Providence = 22 minutes over 32 miles = 87 mph
Providence to New Haven = 91 minutes over 113 miles = 74 mph
New Haven to Stamford = 46 minutes over 39 miles = 51 mph
Stamford to New York City = 45 minutes over 36 miles = 48 mph
Note: The schedule shows a 15 minute stop at NYC....
New York City to Newark = 15 minutes over 10 miles = 40 mph
Newark to Philadelphia = 55 minutes over 91 miles = 99 mph
Philadelphia to Wilmington = 19 minutes over 25 miles = 79 mph
Wilmington to Baltimore = 44 minutes over 69 miles = 94 mph
Baltimore to BWI Marshall Airport = 13 minutes over 11 miles = 51 mph
BWI Marshall Airport to Washington D.C. = 27 minutes over 30 miles = 67 mph
All the math was calculated by (miles/minutes) x 60 = average mph.