Rimutaka Tunnel the first fully dieselised line in New Zealand. Today, DBR, DC, DFT and DX class locomotives run the route. There have been proposals to electrify the tunnel and the Wairarapa line as far north as Masterton as an extension of the Wellington suburban electrification. The tunnel was designed to enable catenary to be installed but this has not happened, and the catenary finishes just north of Upper Hutt station. In 2007, Greater Wellington Regional Council rejected a call to electrify the tunnel, on the basis that patronage did not justify the expenditure, and that the tunnel would "have to be
Otira Tunnel tunnel in the world and the longest in the British Empire. The Midland Railway Company investigated options to a long tunnel; but a line over the pass with gradients of 1 in 50 on both sides was not practical. Other options for a line over the pass were a cable-hauled system or a line of 1 in 15 gradient using either the Fell system or a rack railway using the Abt system (or even a S-shaped tunnel under Mount Rolleston). However the government did not favour the Fell system as used on the Rimutaka Incline which was expensive to operate.