There is a tunnel of 539 metres ( 1767 ft ) near Maoribank , but on the eastern side where two short tunnels ( 220 metres ( 11 chain ) and 180 metres ( 9 chain ) ) had been proposed through a spur it was cheaper to lengthen the line by 140 metres ( 7 chain ) and have open cuttings . The construction of the Rimutaka Tunnel consumed : The first locomotives to work through the tunnel were the 560 kW DG class - the tunnel was too long for steam locomotives , making the Wairarapa Line the first fully dieselised line in New Zealand . Today , 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 made bigger . " Transdev Wellington operates passenger services named the Wairarapa Connection between Wellington and Masterton via the tunnel five times a day each way Monday to Thursday , six on Friday , and twice a day each way on Saturday , Sunday , and public holidays . Excursion trains also go through the tunnel , such as railway enthusiast specials and trains to the Toast Martinborough festival . Steam-hauled excursions require diesel locomotives to provide motive power through the tunnel due to the danger from smoke in the tunnel 's lengthy and confined conditions . From 2014 diesel locomotives hauling passenger trains in long tunnels were required to have fire suppression equipment , following the Pike River Mine disaster enquiry . Initially , DC class locomotives were used for the Wairarapa Connection , then from 2015 , the DFB class was used
Pike River Mine disaster
Pike River Mine disaster
Rimutaka Tunnel