Just saw a special on the worlds fastest vehicals.(History channel) They showed a highly modified narrow gauge rail line at the Holliman High Speed test track. They got a rocket sled to go down the track at 6500 mph pulling 150 G's. It ran on special shoes that locked around the rails instead of wheels. The track was straight and level to within .0025" over it's length. (I think around 5000'). Let's see CSX lay track to that spec.