The calculated distance (air line) between Vanderbijlpark and Piet Retief is approximately 185 miles respectively 297 kilometers.
By car or train, the actual journey to Piet Retief is certainly longer, as only the direct route (as the crow flies) between Vanderbijlpark and Piet Retief has been calculated here.
Air line (approximately)
297 kilometers
160 nautical miles