Just as in Peninsula Malaysia, there are several routes in South Island that take you from the west coast to the east and vice versa. One is in the Southern Alps through Arthur's Pass, attributed to one Arthur Dobson in the 1860's although the Maori had long known of it's accessability to the other side.
As for us, we only wanted to get as far as the village post and see what's there. As usual the GPS guided us through the shorter and scenic but not necessarily the faster route. That day the wind was strong and blustery and whistled through the car windows which we had rolled down a little bit for fresh air. It's no surprise then, would it, that they should name a place there "Windwhistle"? Strong winds are the norm there, presumably.
Part of the shorter route is fair-weather road for a good distance about 30km or so i.e. it is unsealed, hence unusable in very wet or icy conditions. Gravelly road notwithstanding, we came across some of the most starkly beautiful scenery of our holidays, only that the cameras we had couldn't do them much justice.
Single-lane bridges such as in the picture are quite common on South Island roads, even on highways, and are sufficient to handle the traffic volumes.
It decided to rain when we eventually arrived at Arthur's Pass village - we stopped and ducked into the nearest eating place / toilets - "The Merrie Kea"