I rode up on the motorbike. It was foggy and wet in the morning. Great scenery, lots of twisties, and through a waterfall. As the guidebook says, 'Stay alert and you probably won't die'. A good day's ride from La Paz and return.
Road varies from good gravel to no road at all.
There are no petrol stations between Uyuni and Calama.
The Bolivian border station may not be manned so get an exit stamp the day before in Uyuni.
This track is too far to do in a single day unless youre very fast off road but there are guest houses and a small shop on the Chilean side of the border in Ollague. Bring enough food, water and petrol to last the full trip. There are ample wild camping options.