After driving via Cardrona over the crown range to Queenstown, I think I understand the problem.
I cant post my photo but I was standing at the lookout watching a Jetstar aircraft flying down the valley on approach to Queenstown.....below me.
That used to be a fun road to drive over....once upon a time....back when it was a gravel road with no crash barriers protecting motorists from the huge drops over the side. It resulted in bugger-all traffic on the road (the tourists were too scared to drive over it and went the long way around via the Kawerau Gorge instead, and many Kiwis likewise avoided it like the plague), which meant that those of us who actually know how to drive fast on narrow, windy gravel roads could get between Queenstown and Wanaka (and vice-versa) in super-quick time. Then, they upgraded the road, and now it is a slow trip due to all the road maggots (camper vans) and slow-drivers who crawl over the hill.