Hi Pitata
The gravel road up Swartberg Pass is a public road, and can be done with a car. It has some sharp turns and loose stones, so take it slow. The road down to the "Hell" is also no problem unless you speed. There are steep down hills and steep turns. I think that some spots will be slippery when wet. Some spots also have loose stones. This however, is not even a 4X4 route and can be done with a normal bakkie. It is definitely pillion friendly and surely not difficult. Just give yourself a lot of time to spend on the viewing and taking of photo's. It is worth it.