The first section of the journey is the R76 from Kroonstad to Steynsrus. There are potholes on some sections of the road, mainly between Kroonstad and Steynsrus. From Bethlehem to Harrismith the newly rebuilt N5 is a driving pleasure. From Harrismith to Durban the road follows the N3 which can be very busy, especially heavy vehicle traffic that picks up later in the day.
My advice to tourists travelling to Durban from Kroonstad would be to leave very early, have a breakfast at Swinburne past Harrismith and arrive in Durban before lunchtime.