Most of the East Coast passenger railways were laid down when trains were much slower, and even then they had to pass through many densely populated areas. So t

Most of the East Coast passenger railways were laid down when trains were much slower, and even then they had to pass through many densely populated areas. So there are a lot of curves, mostly flat, and lots of surface crossings with roads. That slows the trains down. Some sections have been upgraded to allow higher speeds, but with station stops and unimproved sections the average speed is stilk slow.