The calculated distance (air line) between Asan and Yangp'yŏng is approximately 56 miles respectively 90 kilometers.
By car or train, the actual journey to Yangp'yŏng is certainly longer, as only the direct route (as the crow flies) between Asan and Yangp'yŏng has been calculated here.
Air line (approximately)
90 kilometers
48 nautical miles