Otira tunnel
| Otira tunnel | ||||
|---|---|---|---|---|
| use | Railway tunnel | |||
| traffic connection | Midland Line | |||
| place | between Otira and Arthur's Pass ( South Island (New Zealand) ) | |||
| length | 8550 m | |||
| Number of tubes | 1 | |||
| construction | ||||
| start of building | May 25, 1908 | |||
| completion | 4th August 1923 | |||
| location | ||||
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| Coordinates | ||||
| North portal | 42 ° 51 ′ 45 ″ S , 171 ° 32 ′ 55 ″ E | |||
| South portal | 42 ° 56 ′ 21 ″ S , 171 ° 33 ′ 47 ″ E | |||
Map with all coordinates: The Otira Tunnel is a Midland Line railway tunnel on the South Island of New Zealand , between Otira and Arthur's Pass . Here it pierces the New Zealand Alps with a length of 8550 m. The incline is about 1:33, and the end of the tunnel at Otira is about 250 m lower than the end at Arthur's Pass.
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Construction work began on May 25, 1908, and the contractor was J. McLean & Sons. After the technical difficulties were greater than estimated, the work was stopped in 1912 after only half of the tunnel had been excavated. In 1913 the work was continued by the public sector, the Public Works Department. The tunnel was pierced in July 1918, this was celebrated with an official event on August 21, 1918. The height difference was only 29 mm, the bank angle only 19 mm. The expansion of the tunnel and the installation of the electrical systems took until August 4, 1923, when the tunnel could then be put into operation. At the time, it was one of the longest tunnels in the world and the longest in New Zealand, but has since been replaced in New Zealand by the Kaimai Tunnel and the Rimutaka Tunnel on the North Island.
Due to its length and incline, it was not possible at the time to operate the route with steam, as the danger from the smoke gases that was generated would have been too great for passengers and train staff. For this reason, this section was equipped with a contact wire with 1500 volts DC voltage . A coal-fired power station was built in Otira to generate the necessary electricity. First electric locomotives of the Eo series were used, then from 1968 the EA series.
Following the example of the Otiria Tunnel, the Lyttelton Rail Tunnel was also electrified.
Since the locomotives were obsolete in the late 1990s, the electrical facilities have been removed, the traction is today diesel locomotives of class DX taken.
A combination of fans and a gate was installed at the tunnel portal to ventilate the tunnel . After a train has entered the tunnel near Otira, the gate is closed and the exhaust gases are extracted with fans behind the train. Only then will the gate open again. The TranzAlpine observation cars are not accessible while driving through the tunnel.