Rimutaka Tunnel The first shot was fired in 1948 when the Public Works Department started the tunnel with bores of at the western end and at the eastern end. A contract for completing the tunnel was let to a consortium of Morrison Knudsen Inc. and Downer and Company on 7 May 1951. The work commenced at the west end in July 1951 and at the east end in August. The contract was expected to be completed in four years, but the headings met on 20 April 1954 with the concrete lining finished a month later. New Zealand Railways took possession of the
Rimutaka Tunnel cutting for the new formation completed and the remainder of the track laid. On Thursday, 3 November, the new line was opened and two special trains travelled from Wellington to Speedy’s Crossing to the inauguration ceremony. The deviation's ruling grade is 1 in 70, compensated for curvature. The tightest curve is 400 metres (20 chain) radius. The tunnel rises at 1 in 400 from the western portal to the highest point on the deviation, roughly halfway through the tunnel, and then descends to the eastern portal at 1 in 180. It has an internal height of 5.18 metres (17 ft)