Amtrak has the Penn Station-style boarding at stations as small as Charlotte. It's completely ridiculous to make passengers wait in a line that wraps around the station, just to board a 3- to 5-car train there. There is only one train every few hours in Charlotte and just one wide platform and so there can be no confusion about the wrong train, no concerns about space on platforms and no other grounds for confusion.
I also checked, and before Amtrak, (generally) only Pullman and Metroliner passengers were required to wait in line before boarding. Amtrak's lines are its own invention (largely), even though stations have been crowded, platforms have been narrow and multiple railroads have served stations for decades. New York Central tried an Amtrak-style queue system at Grand Central for some tracks but abandoned the attempt.
Amtrak just does this boarding style to make its personnel's jobs easier, regardless of how customers are inconvenienced.
Last edited by ibrandsguest; Jul 21, 2013 at 1:53 pm