City before emerging into open air near Hung Hom station at ground level. The line then heads southwest into a tunnel after the station and descending underground through and stations (the former having originally being served by the East Rail line, and the track heading northwards through the latter), before returning to ground level (though still fully covered) at Nam Cheong station. The track then runs northwest through a sealed box tunnel just to the north to and under the West Kowloon Highway through Lai Chi Kok Park into Mei Foo station, which has a ground-level/underground hybrid design. Bored tunnels traverse densely populated Kwai Chung and under the Tsuen Wan line towards Tsuen Wan West station on reclaimed land, after which a 5.5 km (3.4 mi) bored rock tunnel, the Tai Lam Tunnel, takes trains through Tai Lam Country Park. The line then emerges into open air just south of the train depot at Pat Heung and initially runs at-grade, and later on an embankment, as it approaches Kam Sheung Road station. The rest of the line is fully elevated and constructed on a continuous viaduct, running in a westerly direction through the new towns of Yuen Long and turning towards the south at Tin Shui Wai, before taking a bend towards the Tuen Mun River and eventually terminating at Tuen Mun station. Construction methods predominantly include tunnel boring machines and cut-and-cover, though the Lion Rock Tunnel between Hin Keng and the Ma Chai Hang Recreation Ground was constructed using the drill-and-blast method. While road and rail traffic in Hong Kong move on the left, the eastern section of the Tuen Ma line is an exception, as trains move on the right between Sung Wong Toi and Wu Kai Sha. This allows the southbound tracks of this line and the East Rail Line to lie opposite each other at Tai Wai, such that cross-platform interchange could be provided there. This design was to speed up passenger interchange between the East Rail Line and Tuen Ma line to Kowloon during the morning commute, although the reverse transfer would require going down to the concourse level and back up again. This layout is maintained as far as Sung Wong Toi, before the line goes into a stacked formation at To Kwa Wan, which has a split platform layout to allow the tracks to switch sides and adopt the left-hand running used on