The nature of the terrain the WPR was built on is rugged by railway terms, with the 12.8 km section through the Weka Pass itself being an almost continuous ruling grade of 1 in 50 (2%). This was a major factor in the decision not to continue the Waiau branch as the South Island’s Main Trunk – a coastal route eventually being favoured.
The Weka Pass Railway is unique in New Zealand as it is the only place where steam locomotives regularly operate on a long and sustained major incline. It is a challenging line to operate, warranting a meticulous driving ability and physically fit firemen.