Guardian: In the vast natural wind tunnel that is Dabancheng, the gales that roar between the snow-capped mountain ridges get so strong that trains have been gusted off railway tracks and lorries overturned. Such is the ferocity of the elements that police sometimes have to stop the traffic that passes through this arid, six-mile-wide plain on what was once part of the Silk Road. That used to be bad for business in Xinjiang, the most westerly region of China, which formerly depended on the …