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.

The line then emerges from the tunnel 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.

KCRC initially ordered 18 sets of 4-car SP1950 trains, built by Kinki Sharyo, running on the Ma On Shan line; they have all since been converted to eight cars.

[15] Up to 26 sets run during the morning peak service with a 171-second headway; MTRC specifies capacities of 52 seated and 286 standing passengers per car.

Both railways were envisaged to be extended in the near future and platforms on the Ma On Shan line were built with reserved structures for extension at a later date.

Both MTRC and KCRC independently submitted their own proposals to the Hong Kong government for developing the Sha Tin to Central Link (SCL) by extending their own existing networks.

Speculation of a "East West Line" arose when a photograph of an info plate printed with "EWL" (東西綫) at Ho Man Tin station while it was under construction surfaced.

The plate was removed before the opening of the station that year as part of the Kwun Tong line extension to Whampoa.

The Tuen Ma line was planned to be fully operational in 2019, but after the newly built platforms at Hung Hom station failed a safety inspection which occurred between December 2018 and January 2019, its full opening was postponed by about two years.

This led to more thorough investigations, hearings and inspections behind the set concrete for assessing if it would require demolition and rebuilding the structure from scratch.

The remaining section of the Tuen Ma line, from Kai Tak to Hung Hom, opened on 27 June 2021.

[22] In May 2020, the Government submitted a proposal for the Tuen Mun South Extension to the Legislative Council Subcommittee on Railway Matters.

Considering that the detailed planning and design of the project will take about two to three years, the Tuen Mun South Extension started construction in 2023 and will be completed in 2030.

Shorter trips occur regularly during peak hours and at the start or end of service: The following is a list of the stations on the Tuen Ma line.