Marton–New Plymouth line

The Marton–New Plymouth line (MNPL) is a secondary railway in the North Island of New Zealand that links the Taranaki and Manawatū-Whanganui regions.

[1] A tramway had originally been considered for the Rangitikei District, but this plan was abandoned in 1872 and surveys for a railway undertaken in 1873.

The route had been chosen due to its cheapness to construct, but its alignment and torturous grades attracted criticism from the day it opened.

[1] From Kai Iwi, Waitotara was reached on 20 September 1880, Waverley on 23 March 1881, and Manutahi via Patea on 28 August 1883.

The next year, construction began on the MNPL south from Sentry Hill after John Brogden and Sons were awarded the contract for the first section in January.

[8] The final section of approximately 16 kilometres from Hawera to Manutahi passed through rugged country and required viaducts over the Tangahoe and Manawapou Rivers.

Due to wet weather, surveying took longer than expected, and in 1882, contracts had still not been let despite the imminent completion of the southern portion to Manutahi.

The Wellington Chamber of Commerce applied pressure on the Public Works Department to prioritise the section's approval, fearing that its construction was in jeopardy and any failure to link the two railheads would be considerably detrimental to both the profitability of the existing railway network and to the wider economy.

[10] The final section was subsequently granted approval and it was not until 23 March 1885 that construction was finished and the through line from Marton to New Plymouth was open for revenue service.

[13] The criticism of the difficult Turakina route south from Wanganui voiced at the opening of the line progressively increased over the years.

Due to the project's importance, work continued throughout World War II, with only a brief pause in 1942 at the height of fears of a Japanese invasion.

However, difficulties on the 1 in 35 grades of the original Turakina route and Westmere Bank meant that the railcars had to have different gears installed, reducing their top speed from 120 km/h to 105 km/h.

[19] Increasing competition from road and air led to a decline in passengers after World War II.

The New Plymouth Express and Taranaki Flyer ran for the last time on 31 October 1955 and were replaced by Standard and 88-seater railcars.

[20] In the early years of the line, freight was primarily local and the railway served as a link between ports and their hinterland.

Nowadays the line sees two-weekday freight services between Palmerston North (departing 2350 and 0355) and New Plymouth (departing 1530 and 1815) and up to three daily return services between Palmerston North and Whareroa, carrying milk from the Manawatu and Hawkes Bay (via a facility at Oringi and rail from there) to the Fonterra plant and empty milk tankers and containerised products on the return trip through most of the year.

When introduced in 1972, the DX class were not common on the MNPL largely owing to the need to strengthen bridges to accommodate their weight.

The peak season milk trains, for instance, were usually hauled by a pair of DX units owing to the weight of these services.