The calculated distance (air line) between Neder-Hardinxveld and Heerlen is approximately 81 miles respectively 131 kilometers.
By car or train, the actual journey to Heerlen is certainly longer, as only the direct route (as the crow flies) between Neder-Hardinxveld and Heerlen has been calculated here.
Air line (approximately)
131 kilometers
71 nautical miles