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
Beaminster Tunnel a white cross which can still be seen "in situ". The tunnel reduced the road's gradient from 1-in-6 (17%) to 1-in-10 (10%) and shortened it by a mile (1.6 km), as well as lowering its maximum elevation by . At the time of its opening, only a handful of road tunnels had been built in Britain; it pre-dates the construction of the first railway tunnels, and it is now the only pre-railway road tunnel in the country still in use. The tunnel was formally opened on 29 June 1832 with enthusiastic celebrations including a 21-gun salute fired from the top