The calculated distance (air line) between Bukit Mertajam and Simpang Empat is approximately 31 miles respectively 49 kilometers.
By car or train, the actual journey to Simpang Empat is certainly longer, as only the direct route (as the crow flies) between Bukit Mertajam and Simpang Empat has been calculated here.
Air line (approximately)
49 kilometers
27 nautical miles