July 2010. Four intermediate new stations, Batu Kentonmen, Kampung Batu and Taman Wahyu were opened with this extension. The Seremban Line was extended from Seremban to Sungai Gadut on 14 May 2011 with an intermediate station at Senawang, and to Rembau in 2013. Northern Sector services were introduced on 11 September 2015 between Gurun in Kedah, Butterworth in Penang and Kamunting in Perak. This followed the completion of the Ipoh-Padang Besar Electrification and Double-Tracking Project in December 2014. On 1 January 2016, a second line was introduced between Butterworth and Padang Besar in Perlis, while on 17 January 2016, the Gurun-Butterworth-Kamunting route was replaced with two separate routes: Butterworth-Gurun and Butterworth-Kamunting. The three-line service operated until 1 July 2016 when the Butterworth-Gurun route was dropped, and subsequently on 1 September 2016, the route took on its current form. Southern Sector services were introduced on 10 October 2015 following the completion of the Seremban-Gemas Electrified Double Tracking Project on 30 October 2013. This service is the second KTM Komuter service outside the Klang Valley after its northern counterpart. The Gemas and Batang Melaka stops were removed starting 20 June 2016 with the train running between Seremban and Pulau Sebang/Tampin. Subsequently, the shuttle service was terminated on 11 July 2016 when it was absorbed into the Seremban Line. From 15 December 2015, the routes of Seremban Line and Port Klang Line were switched as part of a six-month trial. Trains from Seremban began heading towards Batu Caves, while trains from Port Klang headed towards Rawang, and vice versa. Transfers could be done at the four shared stations. The Skypark Link to Subang Airport was introduced on 1 May 2018. Beginning 10 September 2018, all service abolished the cash ticketing system, cashless ticketing method was then compulsory. Stations The Komuter service was largely built from existing lines, with minor alterations (i.e. removal or abandonment of lines and replacement of wooden sleepers with concrete ones). Relevant station platforms were added and heightened to allow easier access to Komuter trains travelling in both directions. Major pre-independence stations including Kuala Lumpur station, Klang station, Port Klang station and Seremban station were retained and upgraded to support Komuter services. Smaller, wood-based stations and halts along the line that were built at around the same time were either demolished and replaced by modern brick-and-concrete counterparts, or simply abandoned. The only exception to the rule is the old Sentul