First up the so called “Tunnel 24” just north of Tuamarina. Contrary to the NZ Railway and Tramway Atlas, alive and well as seen in this video frame from a passing train. There is in actuality no terrain over the top of this tunnel that would justify its existence, and it was not part of the original railway. The best suggestion is that it is an early expression of an overbridge constructed in a tunnel form which are now commonly seen around the countryside, although in no other case are they classified as tunnels, rather as bridges. State Highway 1 is carried over the top of the railway here.
Tunnel 22 is further south, at the summit of the Dashwood Pass. The two small-section tunnels (No.23, formerly No.1 and No.22 formerly No.2) from one of the earliest completed parts of the MNL, the Picton Section to Wharanui, were both daylighted in 1979 and 1981 respectively to bring the line up to modern rolling stock clearances. The Dashwood Pass is a spectacular section of the MNL and one of the major geographical obstacles on the former Picton Section, which was joined to the rest of the MNL only as late as 1942; there is also a major climb between Picton and Koromiko to lift the line over the “Elevation” at Mount Pleasant. In addition, south of Seddon the line drops rapidly down to Blind River. Tunnel 22 was the site of the “Dashwood Smash”, the 1966 derailment of a mixed freight-passenger train in which the locomotives jumped the track and collided with the tunnel; the driver in the lead engine was killed and his assistant seriously injured.