Many thanks to each of you.
With regards to "rules". I prefer to think of them as guides. As guides they are often logical in that they explain how images often best achieve the taker's objective - get the viewers' eyes to step purposefully through the image and see what you were seeing.
In this image I felt that symmetry was important. What I was "seeing" was that everything in that area for so long while driving was the same. The road was straight and the surface the same for about 100kms; the landscape on both sides was filled with the same plant species; the sky was crystal blue... It remained the same for a couple of hours!!
In my mind it was that everything was "symmetrical".... it all just went on and on and on and on... So in the square format, I was compelled to make the image symmetrical so that viewers eyes just followed that straight road through the symmetrical scenery into the horizon.
It seems it worked.
Thanks again. I do find commentaries about the images I post to be helpful.