One consequence of that sudden abandonment is the cobblestone route was left perfectly preserved, frozen as it was a century ago, earning a category one rating from the Historic Places Trust. Another is it was reclaimed by the surrounding forest and soon became impassable. I wouldn't have been able to walk the route at all but for the fact that local people decided to develop it as a walkway.
"When we started thinking about restoring the old road it was completely overgrown," said Dave Scott, the Ohakune car dealer who chairs the local restoration committee.
"We thought we ought to have a look at what we were getting ourselves into so we set out to walk it. Well. It was a heck of an exercise. We had to bush crash. I don't know how we got through. And it's taken a lot of work by a lot of people to open it up again."
In the course of that bush crashing the team rediscovered the old cobblestones and, even more intriguingly, quite a few empty beer bottles.
"That," said Dave, "was an interesting reminder of one of the reasons the coach road got such a lot of use. This was a dry area and those bottles were from the old Taihape Brewery. Obviously it was a sly-grog route as well as a link between the two railheads."
The walking trail already runs about 7km from the lovely old Ohakune Railway Station, via Old Station Rd and Marshalls Rd, and then along the track proper to the two Hapuawhenua rail viaducts, with some excellent information boards telling its stories along the way.
Earlier this year the old viaduct - 43m high, 286m long, and built in 1908 - was restored so you can walk over it and enjoy impressive views of the even larger new viaduct - 43m high, 414m long and opened in 1987 - plus the Hapuawhenua Stream below and the surrounding bush.
At the moment it's an out-and-back walk but the next stage, already well under way, is to carry the track through to the settlement of Horopito on State Highway 4.
Eventually it is intended to be a part of a 245km, four to six day, mountain to the sea cycle route going from the slopes of Ruapehu, via the old coach road and cycle trails in Whanganui National Park, down the Whanganui River - with a jet boat ride at one point - to the shores of the Tasman Sea.
All of this is part of a long-term campaign to promote Ohakune as a summer destination as well as a winter base for enjoying the Turoa Ski Field.
There are already several other walks including the Mangawhero River Walkway, connecting the township to Tongariro National Park and Ruapehu, and the Rotokura Walkway, embracing Dry Lake and Rotokura, a lake sacred to the local Ngati Rangi people.
In addition, pointed out Richard Chittock, co-owner of Ahuru Lodge, where we stayed during our stopover, "there's excellent trout fishing, good hunting, kayaking, offroading and the country's oldest national park. In fact I think it's an even better summer destination than a winter one."
The lodge sits in the countryside a few kilometres outside Ohakune, on the banks of the Tokiahuru Stream, with each room enjoying a magnificent full-frontal view of Ruapehu.
As you come to expect at such lodges the cuisine was excellent. But what interested me was the wonderful local produce they draw on, not just the carrots for which the town is celebrated, but a whole range of goodies.
For instance, the coffee comes from nearby Raetihi, where a local man imports, blends, roasts, grinds and distributes under the brand of Volcano Coffee, guaranteed to be organic and fair trade if such things matter to you.
And in the antipasto we had before dinner there was a marvellous salami, which turned out to have been produced by Waimarino Eco Pork, a company started by a Swiss veterinarian after our crazy rules prevented him from practising his profession. "Why is this?" he is supposed to have asked. "Do your cows have five legs?"
The company also produces excellent sausages and bacon which I enjoyed for breakfast before heading off on the next stage of my rail journey. I doubt the poor devils who put the main trunk line through this rugged country ate half as well.
CHECKLIST
Further information: You can find out about the Scenic Rail Pass at tranzscenic.co.nz.
Ahuru Lodge offers special packages for train travellers.
Information about the Ohakune Old Coach Road is at doc.govt.nz.
Jim Eagles travelled New Zealand by rail with help from KiwiRail, Air New Zealand and the regional tourism organisations along the way.