It's never too cold to work

BMW at the Snow Farm. Photo / Supplied

Cardrona's famous Snow Farm may have its own weather stations, but it can only predict the climate - not alter it.

So when our convoy of xDrive BMWs arrived to find rain had turned the snow to slush, our ice-drive quickly turned to a gravel road fang amid the best of NZ's mountain scenery.

The Snow Farm - officially known as the Southern Hemisphere Proving Grounds - must keep a stern eye on the weather because it relies on clear cold conditions for the three months of the year it's open.

During these three months, the world's vehicle manufacturers conduct cold weather research and testing here. Some 30 companies send 500 engineers with 3000 mostly studless snow tyres and 150 prototype cars.

They develop cold-start systems on one of 12 separate sets of test tracks; fine-tuning snow tyres and brakes, or traction and stability control electronics that will go on to save lives on ordinary roads the world over.

Snow Farm chief engineer Graeme Gambold says each day 3242 people die from car accidents worlwide. Cars are the No1 killer of people aged 10 to 24 and it's set to get worse by 67 per cent before 2020, say some.

Car companies can't do much about driver skill or road conditions but they can improve their cars and try to remove the vehicle factor from the fatality figures.

So a cohort of engineers follows the cold weather around the world, from Alaska, to Canada, to Sweden - with New Zealand plugging the June to August months. Here they test all day, then send the results north each night where engineers write new programs and return them before our sunrise.

Getting the right surfaces on the test tracks and in the ice tunnel is an art in itself; the snow must be fine, smooth and sufficiently compact over a variety of given gradients. Millers and rollers work overnight to prepare the snow for the morning.

The aim is to replicate the exact surface of hard-packed snow roads alongside heated tarmac pads and ice. Snow has half the grip of bitumen; ice a tenth of the grip.

And the BMWs? We did test the clever xDrive system on 15 and 20 per cent slopes clad half in heated tarmac, half in ice. The system uses the ABS sensors on each wheel to rapidly detect spin and reapportion power accordingly, rather than applying brakes. If even only one wheel has grip you will move forward, and we were able to stop and start as efficiently as on more stable surfaces - and negotiate high-speed gravel trails with almost as much confidence as offered by tar.

That such a system exists is thanks to testing facilities like this one; no wonder Gambold is so busy.