Big Hill

The Big Hill on the Canadian Pacific Railway main line in British Columbia, Canada, was the most difficult piece of railway track on the Canadian Pacific Railway's route. It was situated in the rugged Canadian Rockies west of the Continental Divide and Kicking Horse Pass. Even though the Big Hill was replaced by the Spiral Tunnels in 1909, the area has long been a challenge to the operation of trains and remains so to this day.

The essential problem was that the railway had to ascend 1,070 feet (330 m) along a distance of 10 miles (16 km) from Field at 4,267 feet (1,301 m) climbing to the top of the Continental Divide at 5,340 feet (1,630 m). The narrow valleys and high mountains limited the space where the railway could stretch out and limit the grade (hence the later decisions to bore extra mileage under the mountains and lower the grades).

To complete the Pacific railway as quickly as possible, a decision was made to delay blasting a lengthy 1,400 feet (430 m) tunnel through Mount Stephen and instead build a temporary 8-mile (13 km) line over it. Instead of the desired 2.2% grade (116 feet to the mile) a steep 4.5% (some sources say 4.4%) grade was built in 1884. This was one of the steepest railway lines anywhere. It descended from Wapta Lake to the base of Mount Stephen, along the Kicking Horse River to a point just west of Field, then rose again to meet the original route.

Seen as a temporary solution, this grade was twice the percentage normally allowed for a downhill train track. The first construction train to go down the pass ran away off the hill to land in the Kicking Horse River, killing three. The CPR soon added three safety switches (runaways) on the way down to protect against runaway trains. The switches led to short spurs with a sharp reverse upgrade and they were kept in the uphill position until the operator was satisfied that the train descending the grade towards him was not out of control. Speed was restricted to eight miles per hour (13 km/h) for passenger trains and six (10 km/h) for freight, and elaborate brake testing was required of trains prior to descending the hill. Nevertheless, disasters occurred with dismaying frequency.

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