Kaimai Tunnel Kaimai Tunnel The Kaimai Tunnel is a railway tunnel through the Kaimai Range in the North Island of New Zealand. Since it was opened in 1978, it has held the title of longest tunnel, at 8.879 kilometres, in New Zealand, assuming this distinction from the previous title holder, the Rimutaka Tunnel. It is part of the Kaimai Deviation, which was constructed to bypass the old route of the East Coast Main Trunk Railway through the Karangahake Gorge (part of which has been preserved as the Goldfields Railway). The Kaimai Deviation is a 24 km line between Waharoa and Apata, including
Rimutaka Tunnel the former route's Pakuratahi Tunnel. The 117 metre (380 ft) high shaft was constructed after tests showed that the tunnel would not generate enough natural ventilation if diesel traction was used through the tunnel. Originally it had been envisaged that electric traction would be used by extending the 1500-volt DC overhead electrification beyond Upper Hutt to either Featherston or Masterton, but economic studies favoured diesel traction. The new formation included two crossing loops; at the new Maymorn Railway Station (116 wagons) and the Rimutaka Loop (95 wagons) at the eastern portal of the tunnel. There are four bridges including a