The MRT Sungai Buloh–Kajang line is the ninth rail transit line and the second fully automated and driverless rail system in the Klang Valley area, Malaysia after the Kelana Jaya Line. It is a part of Greater KL/Klang Valley Integrated Transit System. The line is numbered 9 and coloured green on the official transit map.

It is one of three planned rail lines under Klang Valley Mass Rapid Transit Project by MRT Corp. The Phase 1 between Sungai Buloh and Semantan commenced service in 16 December 2016. Phase 2 of the line will begin on 17 July 2017, as confirmed by Malaysian Prime Minister Dato' Seri Najib Tun Razak.

The MRT Sungai Buloh–Kajang line is the first of the three planned Klang Valley Mass Rapid Transit lines to be constructed, with estimated contract value of MYR36 billion.

The line starts from Sungai Buloh which is located to the north-west of Kuala Lumpur, runs through the city centre of Kuala Lumpur, and ends in Kajang, a fast developing town located to the south-east of Kuala Lumpur. The line serves a corridor with an estimated population of 1.2 million people.

Phase One of the MRT Sungai Buloh–Kajang line from Sungai Buloh to Semantan had become operational at the end of 2016 while Phase Two from Semantan to Kajang will become operational by July 2017, allowing trains to serve the entire line. Part of Phase one, between Sungai Buloh and Semantan, commenced service in December 2016.

Announced in 2006, the line was initially planned as a LRT at 43 km in length, linking the densely populated areas of Damansara in the northwest and Cheras in the southeast, through the central business district of Kuala Lumpur city.The government then decided to extend the alignment at both ends to Sungai Buloh and Kajang respectively, adding 8 km to the line for a total of 51 km. In addition, the line was changed to an MRT system, with higher capacity trains.

...
Wikipedia