Welcome to Spain, the A is mostly used to autovías or autopistas but they can be to carreteras convencionales,, there are many hidden highways on Spain, bc they can start with different letters!
At first, I thought that was sand, but when I looked closer, I noticed the sides of the greenhouses. What do they grow in them? I suspect that is where most of Europe gets their fruits and vegetables out of season from.
What on earth do they need greenhouses for in southern Spain? You can very easily grow citrus fruit there. Whatever the reason, it makes for a surreal landscape.