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Construction of the Spiral Tunnels commenced in 1906 with completion in 1909.

The tunnels were constructed to replace the 4.5 % grade of the Big Hill with a

gentler grade of 2.2 %. Alternative solutions to grade reduction were

considered, namely following the east and west slopes of the Yoho River to the

north or maintaining a longer grade on the south side of the Kicking Horse River

passing Field at a higher elevation. But it was concluded that both of these

solution posed too high a risk for avalanche and mudslides.

J. E. Schwitzer, one of the railway’s Assistant Chief Engineers, came up with the

idea of two Spiral Tunnels. After cresting the Kicking Horse Pass a westbound

train proceeds to the 3255-foot Upper Spiral Tunnel.  Also known as Spiral Tunnel

#1 the train completes a 3/4 of a circle left-hand turn in Cathedral Mountain

emerging 56 feet lower. After descending to the northeast the train enters the

2922-foot Lower Spiral Tunnel (Spiral Tunnel #2) were it completes a two-thirds

of a circle right-hand turn. It emerges 50 feet lower again heading west towards

Field, British Columbia.

As many as 30 trains a day pass through the Spiral Tunnels. The lowering of the

grade increase the efficiency of eastbound locomotives, while improving safety

for westbound trains as they descended the hill. Cost savings were realized by

allowing the removal of many helper locomotives from dedicated service at

Field and Laggan (now Lake Louise).

Westbound grain train at the Spiral Tunnels, July 2007

Westbound train at the Spiral Tunnels, May 2010

Spiral Tunnels from the from rear car on Rocky Mountaineer, September 2010.


Posted: January 25, 2013


The Spiral Tunnels


Eastbound unit grain train exits the upper portal of the Lower Spiral Tunnel and wraps around

on itself on its way to the Upper Spiral Tunnel.


September 3, 2007


Panorama of the Spiral Tunnels. 1908