ON THE CLIMB: KiwiRail Freight up the Raurimu Spiral (4K) 

The Raurimu Spiral near National Park, New Zealand, is an engineering masterpiece of the 20th century. Originally devised in the 1880s was a 20km detour route of the North Island Main Trunk which had nine tall viaducts and a ruling gradient of 1 in 50, and even steeper in some areas.
In 1898, surveyor Robert Holmes proposed the current route. The final design involved a gradient of 1 in 52, two tunnels, and overlapping tracks forming the spiral.
Leading to today, the Raurimu Spiral sees daily freight services from KiwiRail, usually servicing between the two large cities of Auckland and Wellington. We see a heavy train 225 on the ascent of the spiral, in notch 8 most of the way up.