Awesome stuff Frank. I've enjoyed seeing how this progressed. My super critical comments would be.
I actually like the flowers you've put in. Just not so close to the road. That little bit of colour in the mid ground really convinvces you that 'this isn't the CG I'm looking for'. Heather has that colour flower. When you see the same model on the road side, that's when the game is given away I think.
From where the sun is, I can understand the car window choice. Difficult one that. In reality I guess, you wouldn't see anything at all, except perhaps very subtle smears in the specularity/refraction. The rest of the texturing looks right. The paint looks waxed. The tyres, dusty and matt. Shiny alloys?
The transition from tarmac into stones looks a little soft. I wonder if there's a way to get a sharp fall off with a 'cracked' plan mask. The bumps look right.
The repair lines in the road look a little too 'wet' in this environment. But in reality I guess, the tarmac would melt and reflect as you have it. Nice touch.
The road could be smoother.

(The method Ive found, I'll gladly post at some stage, doesn't work with pre displaced landscape. It has to work in colour space before you displace the landscape. Which is a different way of working.)