The first Klang Valley MRT line is the 51km MRT Sungai Buloh-Kajang Line. 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.

Phase One of the MRT Sungai Buloh-Kajang Line from Sungai Buloh to Semantan will become operational by the end of 2016 while Phase Two from Semantan to Kajang will become operational by July 2017, allowing trains to serve the entire line.The line will have 31 stations of which seven will be underground. The line will be underground for a distance of 9.5km.

PAB is responsible for Phase One of the MRT line which is from Sungai Buloh to Semantan, a total of 12 stations under this phase.