I have just come back home from my conference in Athens, GA. Total door-to-door travel time, from the hotel to my apartment: just under 8 hours. The road distance from Athens to New York is about 1,300 km, so the average speed is barely higher than that of the East Coast Main Line between London and York, and lower than that of modern high-speed rail even including connections at both ends.
The main factor raising travel time so much was getting to the airport in Atlanta. Athens-Atlanta is served by arterial roads with some grade separation, but not Interstates; the total travel time is about an hour and a half, and another 15 minutes to the airport. Add shuttle van schedule padding, much uncertainty about security, and very long legacy airline boarding times, and door-to-departure was 4 hours.
This lack of Interstate connection is part of what makes this a realistic option for rail. I do not know specifics about the freight railroad connecting Atlanta and Athens except that it’s owned by CSX and only moderately curvy, but if it were reactivated as modern intercity rail, it would be successful. It’s 111 km from Athens to Downtown Atlanta; 1:22 city-to-city (3 trains provide hourly service) making multiple stops along the way would be unambitious, and 1:22 Athens-to-Atlanta-to-the-airport would be feasible. UGA students traveling home or to Atlanta would flock to it.
Every time I fly domestically even somewhat beyond the optimal range for high-speed rail, I temporarily stop caring about cost-effectiveness and want fast trains, now. With this caveat, let me note that New York-Atlanta in 5 hours is ambitious, but possible. For me, it would mean the Atlanta-Athens line could get me home in about 7 hours door-to-door, by either train or plane. And if the preferred route from Charlotte to Atlanta detoured to the south to serve Athens, it would cut away the connection time and make the entire run take about 5.5 hours.
Of course, it requires either overcoming a lot of agency inertia or spending huge sums of money to build high-speed rail just down to Washington; building to Atlanta requires both. Even if the US could bring costs down to French or Belgian levels, Washington-Atlanta would cost nearly $30 billion. But once built, the line would be competitive even for trips that do not make use of Atlanta’s meager existing connecting transit. The value may end up higher than the cost of construction. And connecting transit on modernized legacy track should not be technically difficult to add.