TranzAlpine

The TranzAlpine crosses New Zealand's South Island from sea to sea in a single morning. It leaves Christchurch's Addington station on the Main South Line, runs 20 kilometres (12 miles) south-west across the Canterbury Plains to Rolleston, then swings north-west onto the Midland Line, 212 kilometres (132 miles) of railway that took two owners and forty-one years to finish. Ahead lie Darfield, Springfield and the wall of the Southern Alps.

Past Springfield the line begins to climb and the engineering starts. Rather than cut a new grade, the surveyors followed the pre-cut channels of the Waimakariri and Broken River gorges, which meant fifteen short tunnels and four viaducts in barely twenty kilometres (twelve miles). The Staircase Viaduct, opened in 1906, carries the track 72 metres (236 feet) above the stream on a 149-metre (489-foot) span; the Broken River viaduct of the same year stands 55 metres (180 feet) high; and Pattersons Creek is the longest of the group at 186 metres (610 feet).

Cass, a cluster of railway sheds on the open tussock, is the most painted railway station in the country. Rita Angus made it the subject of her 1936 canvas Cass, voted New Zealand's greatest painting in a 2006 television poll and held today by the Christchurch Art Gallery Te Puna o Waiwhetu. Beyond it the train reaches Arthur's Pass at 737 metres (2,418 feet), the highest working railway station in New Zealand, in a valley named for Arthur Dobson, who mapped the crossing in 1864 along an ancient pounamu trading route.

From Arthur's Pass the railway does not climb the pass at all: it goes under it. The 8.566-kilometre (5.323-mile) Otira Tunnel, begun in 1907 and opened in 1923, falls continuously at 1 in 33 through the Main Divide and was the longest tunnel in the British Empire when it opened. The train enters in Canterbury light and emerges in a different country: beech forest, rain and the green valleys of Otira. The last stretch runs past Lake Brunner, the largest lake on the West Coast, and down the Grey valley to Greymouth, 223 kilometres (139 miles) and about four hours fifty minutes from the start.

Very few railways cross a country's entire mountain spine and reach open ocean on both sides inside five hours. The TranzAlpine does: braided riverbed and dry tussock on the Canterbury side, temperate rainforest and old coal country on the West Coast, with the Main Divide in between. The contrast is not gradual. It happens inside the 8.566 kilometres (5.323 miles) of the Otira Tunnel, and passengers who go in under Canterbury sun regularly come out in West Coast rain.

The route is also a monument to a nineteenth-century obsession. The East and West Coast Railway League was formed in 1882 to force a crossing; a Royal Commission chose the Waimakariri valley and Arthur's Pass line in 1884; the private New Zealand Midland Railway Company was floated in 1886 and had built only about 120 kilometres (75 miles) before the government seized the works in 1895. No train ran through from Christchurch to Greymouth until the Otira Tunnel opened in 1923, forty-one years after the League first met.

For the traveller, the open-air viewing carriage is what separates the TranzAlpine from a good window seat. It is an unglazed van open to the weather, and it is where the gorge photographs are taken: the Staircase and Broken River viaducts pass directly beneath it, and the train is slow enough through the gorges to work a camera properly.

Two classes run on every service. Scenic is the standard product: large panoramic windows, power sockets at the seat and access to a cafe carriage. Scenic Plus adds extra-legroom reclining seats in a dedicated carriage and a seasonal menu the operator describes as inspired by the Canterbury Plains, the Southern Alps and the West Coast, cooked in a purpose-built kitchen car and served at the seat with drinks included.

The consist is distinctive. Great Journeys New Zealand runs four to six AK class panoramic carriages, one or two AKC cafe cars, one or two AKV open-air observation vans and an AKL luggage van, hauled by DX class diesel-electric locomotives on 1,067 mm (3 ft 6 in) track. Seats are allocated at check-in rather than at the time of booking, so arriving early matters if you care which side you sit on.

Which side? Heading west from Christchurch, the right-hand side has the better of the Waimakariri gorge; coming back east from Greymouth, take the left. Heavy bags are checked into the luggage van, so keep a jacket and your camera with you in the cabin: the open-air van is unheated and exposed, and Arthur's Pass sits at 737 metres (2,418 feet).

The idea of a railway across the Southern Alps arrived long before the money to build one. The East and West Coast Railway League formed in 1882 to lobby for a crossing; in 1884 a Royal Commission settled on the direct route up the Waimakariri valley to Arthur's Pass; and in 1886 Nelson and Canterbury interests floated the New Zealand Midland Railway Company to build it. The company managed roughly 120 kilometres (75 miles) before its finances failed, the government took possession in 1895, and by 1900 it held the whole works, with rails reaching Otira from the west and Broken River from the east.

Progress east of the divide was slow and costly. Trains reached the temporary Broken River terminus in 1906, Cass in 1910 and the township of Arthur's Pass in 1914. Only the tunnel was left, and it took sixteen years: boring began in 1907 and the 8.566-kilometre (5.323-mile) Otira Tunnel opened on 4 August 1923, electrified at 1,500 V DC from the first day because steam could not safely work a bore that long at 1 in 33. The overhead came down on 1 November 1997, after seventy-four years of electric haulage.

The named passenger service is far younger than the line it uses. The TranzAlpine began on 22 November 1987 under InterCity Rail, passed to Tranz Scenic in 1995, to KiwiRail Scenic Journeys in 2012, and to the Great Journeys New Zealand brand thereafter. It carried 204,000 passengers in 2006 and around 130,000 a year by 2016.

The hard kilometres lie between Springfield and Cass, where the railway follows the Waimakariri and Broken River gorges instead of fighting them. Fifteen short tunnels and four viaducts were needed to hold a workable grade on ground that is steep, loose and constantly cut by tributaries. Counting the Otira bore, the Midland Line carries sixteen tunnels in all.

Three of the viaducts date from 1906. Staircase is the tallest, lifting the track 72 metres (236 feet) over a 149-metre (489-foot) crossing; Broken River stands 55 metres (180 feet) high and 133 metres (436 feet) long; Pattersons Creek is lower at 37 metres (121 feet) but the longest of the three at 186 metres (610 feet). A fourth, the Kowai viaduct, sits at the eastern foot of the climb.

The Otira Tunnel is the set piece. At 8.566 kilometres (5.323 miles) it was the longest tunnel in the British Empire when it opened in 1923, and it remains unusually steep for its length, falling continuously at 1 in 33 (3 per cent) from the Arthur's Pass portal at 737 metres (2,418 feet) toward Otira. Because a loaded train would have filled the bore with exhaust, the tunnel was wired at 1,500 V DC from the day it opened and stayed under electric haulage until 1 November 1997.

The TranzAlpine runs year-round, seven days a week, with no service on Christmas Day, and each season shows a different mountain. Winter, June to August, puts snow on the Torlesse and Craigieburn ranges down to the tussock line and gives the classic photograph, but daylight is short and the eastbound return finishes late in the day.

Spring, September to November, is the strongest all-round window: snowmelt fills the Waimakariri and Broken River, the braided channels run milky blue, and the alpine basins above Arthur's Pass come into flower. Summer, December to February, is the busiest, warmest and driest on the Canterbury side and the best time to spend the crossing in the open-air van. Book weeks ahead in that window, because the train is seating-only and does sell out.

Autumn, March to May, brings settled air and the clearest long views up the Waimakariri headwaters toward Mount Binser. Whatever the month, remember that the two ends of the line have different climates: the West Coast is far wetter than Canterbury, and a bright departure from the plains tells you nothing about the weather waiting on the far side of the Otira Tunnel.

Booking is compulsory. Great Journeys New Zealand states that its trains are seating-only and cannot take walk-on passengers once full, so buy ahead, and buy early for Scenic Plus, which runs in a single dedicated carriage on each train.

Check in at least twenty minutes before departure. The Christchurch station at 35 Troup Drive in Addington opens at 07:00 for the morning TranzAlpine and has free all-day parking, which is what makes the return day excursion practical. Greymouth station is at 164 Mackay Street at the town-centre end, where InterCity coaches connect onward for Nelson, Franz Josef and Fox Glacier.

Seats are assigned at check-in and not at booking, so ask at the counter if you want the right-hand side westbound. Large bags go into the luggage van, so keep a warm layer and your camera in the cabin for the open-air van. One practical quirk: the operator does not publish a timetable on its website, directing travellers instead to the booking engine or to its automated line on 0800 872 467, so confirm your times when you book rather than trusting a third-party schedule.