I have a theory. I don’t know this for sure, but I will write it with great authority and expect you to buy into it.
The outback winds constantly blow the red dirt across the highway. Then the monsoon rains flood the low-lying plains and wash red mud across the highway. Before you know it, the roads take on the color of the surrounding dirt.
What is the Grid sign announcing? Your rad, red roads remind me of Kauai. I had red spatter marks up the back of anything white from wearing flip flops (aka slippers on Kauai) when I lived there. Because of the red dirt and the frequency of wet situations, flip flops and white are a match made in bleach heaven.
The grid is a cattle crossing. You know, one of those metal grates that cattle refuse to walk across. Jamie and I have laughed about them because the cattle can easily walk around them on either side of the road, so we don’t quite understand their purpose.