Road travel in South Africa is very abundant, distances are lengthy and remoteness is a possibility. Make sure your medical cover incorporates preferably private medical assistance and airlift medical response. Before you leave make sure you have all your medical insurance documents in a place easily found in the event you are not able to explain you have full coverage. If the first emergency personal to a scene cannot find evidence of medical insurance you will be taken in a State ambulance to the nearest State health care facility. Under the circumstances this is not preferable as private health care which is comparable to the any top facilities in the world is what you really need.
For peace of mind, make sure your medical insurance will cover all eventualities. Travelling into Africa may have hidden exclusions which you will not want to find out about only when a situation arises.