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 and a width of 4.68 metres (15 feet 4 inches); it is lined with concrete with a minimum thickness of 38 cm (15 inches) inside the face of the excavation. When the tunnel holed through on 20 April 1954 the surveying error was found to be only 44.5 mm (1.75 inches). The tunnel was planned to reduce the distance between Upper Hutt and Featherston from to . After its completion, a 2.74 metre (9 ft) diameter vertical ventilation shaft was driven up from a point almost halfway through the tunnel. It reaches the surface beside the Remutaka Rail Trail near