RP questionable gravel roads, off the top of my head three Sanpark's fall into that category, we have travelled those.

Richtersveld, Kgalagadi and Namaqua (all 4x4 apart from Kgalagadi which only has a couple of genuine 4x4 roads ) Tankwa Karoo wrecks your tyres on those sharp pebbles..A month ago I was in Addo and the roads were shocking and I was glad I had my Hilux there and not a personal Saloon car ..Avis would handle it though