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
Wairarapa Line North Island Main Trunk section between Wellington and Palmerston North. The line originally included the famous Rimutaka Incline, which used the Fell mountain railway system to cross the Rimutaka Range between Upper Hutt and Featherston. In the mid-1950s, the line between Petone and Featherston was substantially realigned, with the line diverted to the east of the Hutt River between Petone and Haywards to serve new housing developments in northern Lower Hutt, and the construction of the Rimutaka Tunnel to replace the Rimutaka Incline. Part of the former route west of the Hutt River has been retained as the Melling Branch.