Loading ...That was the best (nay… ‘only’!) documentation I’ve seen of the spiral tunnels. Clicking on the picture brought me to even more documentation of the tunnels, including terrain maps. Interesting that the ‘old line’ needed a 4.4% grade which is killer to a heavy train, and sometimes to the crew also. The redesigned switch-backs with spiral tunnels at each end took the grade down to a manageable 2.2%. As an aside… US railroads have abandoned routes of 3% grades such as Tennessee Pass in Colorado and Raton Pass in New Mexico. Raton is now only used once a day by the Amtrak Southwest Chief. It’s just not economical to send freight over those steep hills.
The CPR did an amazing job of engineering the terrain back in 1909 for Kicking Horse Pass.