Check out the size of the Salt Flats of Salar de Uyuni, compared to the area of the Auckland Region. It measures 150km long, over an area of 3900sq.

I am guessing that if both brakes and parachutes fail at the end of the streamliners run , they can just keep on cruising and enjoy the view. Then wait some time for the support cars to come get them.

The lines on the second pic are options where the expected track will be situated .

The dot? Probably where the car might have to be amphibian