Key Points:

The whitebait season had not been running long when we planned a southern coast-to-coast excursion in search of the ultimate West Coast delicacy.

Despite reports of a poor start to the season and low net numbers, we were optimistic. Grandparents from Timaru and grandchildren from Auckland also wanted to see parts of the countryside not visited for a year. And we wanted to travel without the hassle of anyone having to drive. Toll's TranzAlpine was the best way to go.

Friends had invited us to their high country station, so the most convenient boarding point for this rail journey was Springfield, the township at the foot of the Southern Alps which is also home to an austere but grand Rewi Alley memorial.

The late farmer, teacher, social reformer, peace activist and writer, who spent most of his life in China, was born in this tiny Hurunui District town and his memorial stands near the railway station.

Passengers who boarded the TranzAlpine at Christchurch had already been riding the iron rooster for an hour across the plains, through Rolleston, Kirwee, Darfield and Sheffield.

Toll had booked us a four-seat berth so we settled in for morning tea as our carriage glided quietly out of Springfield.

The TranzAlpine was facing the soaring Torlesse Ranges and headed into some of the trip's most spectacular alpine scenery. Westward-bound with two diesel engines to haul us through one particularly steep tunnel beneath the Southern Alps, we flew past the tiny red railway shed at Cass. This station was made famous in the 1930s by the Rita Angus painting which hangs in the Christchurch Art Gallery. The tiny weatherboard building was repainted by a rail heritage group to emulate the colours seen by the artist. Art mimicked life, now life imitates art.

The awesome Waimakariri Gorge at the border of the ranges is so vast that cars headed towards the mountains on the opposite side of the braided river system appeared as toys.

The first of 16 tunnels loomed as we headed for the Staircase Gully Viaduct where the train slowed to traverse a set of rail bridges perched high above the narrow river valleys: Big Kowai 20m above the Waimakariri riverbed, Patterns Creek 37m, Staircase Gully 72m, Broken River 55m and Slovens Creek 39m.

When we reached the alpine village of Arthur's Pass at the trip's highest point of 737m above sea level, more than half our carriage cleared out. American, Asian and European tourists donned extra layers for their mountain treks and posed in front of the A-line, stone-faced train station.

Some trampers were headed for the Devil's Punchbowl Falls, a 40-minute walk through beech forest from the township named after Arthur Dudley Dobson who discovered a route through the mountains for a coach road in March, 1864. This is most definitely the mid-point in the coast-to-coast traverse across the backbone of the South Island.

Trampers set off as our carriage floated out to descend a breathtaking 359m along a 12km stretch towards the next station, Otira, the first settlement west of the alps.

Now we entered one of the country's engineering marvels. It takes 15 minutes in the pitch black for the train to travel through the 8.5km Otira tunnel. We pressed our faces to the glass, hands cupped against the light, to get even a tiny glimpse of the sheer rock walls that are hidden to all but train travellers under this country's tallest mountain range. Could we feel the train going downhill? we wondered. Not really. The gradient is 1:33 and it felt flat. The observation cars were closed for this leg because of diesel fumes in the tunnel.

The tiny West Coast hamlet of Otira crouched under the mountains is steeped in rail history. Its sturdy square weatherboard Post Office is the holiday home of a friend and was the scene of a late December lunch two years ago as the mountains came alive with waterfalls, the rain poured, roads slipped and we wondered if we would ever see the East Coast again.

Only a few kilometres on, the train passes Jackson and then joins the spectacular Taramakau River, home to salmon and hopefully, teeming with whitebait. We crossed this Tasman-bound waterway just before Inchbonnie which gets 6m of rain annually. Perhaps it deserves a more metric moniker?

Lake Poerua and Rotomanu flashed by but suddenly the trout-filled Lake Brunner came into view shimmering through the beech forests. This is the largest lake on the trip. Rusting pieces of old structures and machinery mark the Brunner coal mine and languish as a sad reminder of New Zealand's worst coal mining disaster in 1896 when an explosion killed 65 men and boys.

Old mining remnants, swing bridges and carpets of green forest all sped by before we saw regenerating rainforest between Kotuku and Moana.

Greymouth was just a few minutes away, as we passed Stillwater, headed for the Grey River which on this warm 20C spring day appeared a deep blue.

We had exactly one hour in Greymouth and, as luck would have it, the Greymouth Evening Star was rolling off its presses behind plate glass windows in full public view.

Just a block away, a cafe was selling whitebait patties at $3 each. It seemed like a good afternoon tea with a glass of wine from the buffet car, so as we climbed aboard the TranzAlpine just after 1pm to head back for the alps and Springfield on the other side, we asked the staff if the morsels could be heated up.

"Yes, but there might be one less patty left when they come out of the microwave," said the buffet car attendant.

Tranzalpine railway history
The coast-to-coast mid-South Island railway link dates back 118 years.

Roy Sinclair's book, The TranzAlpine Express, says work on the line started in 1888, reached Arthur's Pass from the east in 1914 and Otira from the west in 1900. But it was another 23 years before the 12km stretch between those two lines was finished.

The 8.5km Otira Tunnel was bored through the Southern Alps and opened on August 4, 1923, when it became the longest rail tunnel in the British Empire and the seventh-longest in the world.

Today, Otira is New Zealand's third-longest tunnel after the Kaimai and Rimutaka tunnels.

Travel information
Toll's TranzAlpine travels Christchurch-Greymouth-Christchurch in one day, departing Christchurch Railway Station 8.15am, returning 6.05pm.

The line between Christchurch and Greymouth is 223.8km and has 16 tunnels and five viaducts, the highest being the Staircase Gully, 73m above the river.

Open-air observation carriages are open for all but the Otira Tunnel leg of the journey. There's a periodic, quirky commentary - but only in English - which lacks enough detail to fully inform people about what they are seeing.

Day excursion fares are $182 return per adult. Full fare one-way is $130. Discounts for seniors and children.

Further information
See website link below for more information.