Section 2 from Pasar Seni to Terminal PUTRA (now known as Gombak), which includes Malaysia's first underground railway, commenced operations on 1 June 1998.

On 29 August 2006, Malaysian Deputy Prime Minister Dato Seri Najib Tun Razak announced that the western end would be extended to the suburbs of Subang Jaya (USJ and Putra Heights) to the south-west of Kuala Lumpur.

The expansion plan would also see the LRT Sri Petaling Line extended to the suburbs of Puchong and the south-west of Kuala Lumpur.

[14] On 14 April 2016, Prasarana Malaysia confirmed in a media release that the Kelana line extension would be fully operating on 30 June 2016.

[citation needed] At 46.4 km (28.8 mi) in length, it is one of the longest fully automated driverless metro lines in the world.

Of the 37 stations, 31 are elevated, Sri Rampai lies at ground level, and five stops (Masjid Jamek, Dang Wangi, Kampung Baru, KLCC, and Ampang Park) are underground.

Elevated stations, in most parts, were constructed in four major styles with distinctive roof designs for specific portions of the line.

Stations with island platforms allow easy interchange between north-bound and south-bound trains without requiring one to walk down or up to the concourse level.

The stations were built to support disabled passengers, with elevators and wheelchair lifts alongside escalators and stairways between the levels.

[citation needed] In contrast, handicapped-friendly facilities for the Ampang and Sri Petaling Lines were installed beginning in 2012.

Proposed interchange with  ECR  East Coast Rail Link Exit to The Intermark Mall and The Linc KL.

They were equipped with Linear Induction Motor (LIM) propulsion technology which allowed for operation on tighter curves, with less noise and greatly reduced wheel and track wear.

Since its launch in 1998, the ART rolling stock has remained relatively unchanged; only more holding straps have been added and the labeling has been modified from Putra-LRT to Rapid KL.

It will form part of the simulation site at Pulau Meranti for the Malaysian Search & Rescue Team (SMART) to train on.

On 13 October 2006, Syarikat Prasarana Negara signed an agreement with Bombardier HARTASUMA Consortium for the purchase of 88 Innovia ART 200 cars (22 train sets of 4-cars), with an option for another 13, for RM1.2 billion.

[21] The 22 train sets, initially targeted to be delivered from August 2008 onwards, would have four cars each, boosting the carrying capacity of the fleet by 1,500 people.

On 7 October 2007, Syarikat Prasarana Negara exercised its option to purchase an additional 52 Innovia ART 200 cars (13 train sets of 4-cars) for €71 million.

[citation needed] Rapid Rail said that the trains will only be usable by September 2009 after having sufficient rolling stocks, power line upgrades, and safety testing.

[23] Transport Minister Datuk Seri Ong Tee Keat said in Parliament that the new trains would begin operations by December 2009.

[24] However, in July 2009, Prime Minister Najib Tun Razak announced that the four-car trains will only be fully operational by the end of 2012.

[26] In addition to increased capacity up to 950 passengers per trip, new features included seat belts for wheelchair-bound travelers, door alarm lights for hearing impaired, and more handles for standing commuters.

Under the Kuala Lumpur Additional Vehicle programme, the first new generation Bombardier Innovia Metro 300 started service on 29 December 2016.

[32] Each driverless train features a new design for the end caps, a curved sidewall structure, and a larger, more spacious interior.

Low energy consumption is achieved through a combination of lightweight aluminium car shells and a LIM propulsion system.

In addition, the trainsets are equipped with 16 cameras on board, infotainment LCD screens, dynamic route maps, better air-conditioning and bigger windows.

[note 2][40] Due to recent developments in numerous breakdowns involving the 4-coach ART 200 fleet,[41][42][43] it was revealed by Rapid KL that mid-life refurbishment is to be done on the 34 trains.

[note 3] According to former Transport Minister Wee Ka Siong, faulty or dated equipments included tachometers, electronic units and antennas.

[citation needed] On 12 December 2006, an accident occurred during peak hours as a train was approaching Pasar Seni LRT station.

RapidKL resolved the problem by updating the software of the faulty ATC device, and train service resumed as usual on 6 November 2022.

[51] After the subsequent stability tests under the supervision of technical experts from Thales Group and Land Public Transport Agency, the Ampang Park-Kelana Jaya stretch re-opens on 14 November 2022, two days earlier than expected.