This has extended Line 1 to 24.5 kilometres with 19 underground and 1 surface stations in between.At the 13.5-kilometre (8.4 mi) southern end of Line 1, two separate tunnels, each with a diameter of 6 metres (20 ft), were constructed, with the rest was built as a double track cut-and-cover tunnel. Stations in shallow underground sections have side platforms, while deep-level stations have island platforms.