The Ōhakune Old Coach Road provided an all-weather road link for coaches carrying passengers and goods between the two railheads of the North Island main trunk line. With progress on completing the North Island main trunk rail slow, the road provided a way to allow through traffic, until the railheads were finally linked in 1908.
It mostly followed the route (with the exception of the section to Taonui Viaduct) of a bridle track completed in 1886 that had been upgraded to a dray road in 1895. Between 1904 and 1906 it was upgraded, being mostly paved with setts (rock pavers), giving it a durable, all-weather surface for heavy horse-drawn traffic. It was completed in November 1906, at a point when the distance between the railheads was 39 kilometres.
The road was used until early 1909 and after the opening of State Highway 49 fell into disuse. It remained mostly untouched since, though some sections have been lost through deviation of the railway in 1987.
The road can be considered a most significant example of roading engineering heritage and the finest rural road constructed in New Zealand up to that time. It has great historic significance for the period it was used as the link between the two ends railheads. The end of the road’s useful life froze it in time and, other than the natural deterioration it has undergone since its use stopped, it is in remarkably good condition. It has a Category I Historic Places status from Historic Places Trust.
The department, in conjunction with Ōhakune 2000 has re-opened the Ōhakune Old Coach Road as a cycle trail, which forms part of the Ruapehu-Whanganui Trail. When completed, this trail will take cyclists through the Tongariro and Whanganui National Parks, past the famous Bridge to Nowhere, the Hapuawhenua Viaduct and many marae along the Whanganui River Road.
The Hapuawhenua Viaduct was built in 1907-1908 as part of the final works to finish the North Island main trunk railway.
It was designed by Peter Seton Hay, Superintending Engineer of the Public Works Department, recognised as one of the most influential engineers of the period. The viaduct has a Category I Historic Places status from Historic Places Trust.
The viaduct consists of 13 concrete piers and four 4-legged steel towers resting on concrete foundation blocks. There are four steel plate girder tower spans of 11 metres, five 20 metre lattice truss spans and thirteen 11 metre plate girders. In total the viaduct is 284 metres long and at its maximum it stands 45 metres high. It is unique in that it is built on a 10-chain radius curve, reflecting the difficult landscape through which it passes.
Workers lived on site during the two years it took to construct the viaduct, enduring harsh winters, primitive conditions and isolation to complete construction in time for the opening of the railway.
The Hapuawhenua Viaduct was in use until 1987 when the line was realigned and a new viaduct was built. It is mostly in original condition, and is currently being restored by DOC and Tongariro Natural History Society to allow visitors to again enjoy this spectacular piece of railway engineering heritage.
The Taonui Viaduct shares many of the features of the nearby Hapuawhenua Viaduct: it was also designed by Peter Seton Hay, shares the same construction methods, and unique curved style. It practically differs only in its smaller size (140m long and 35m high), aspect, and fact that it is built on a 1 in 60 gradient.
The viaduct has a Category I Historic Places status from Historic Places Trust.
At this time, the Taonui Viaduct will not be restored for visitor use. Access to view the viaduct is being restored as a side track of the Old Coach Road.