On December 9, 2007, an express service began to run on Line 4 at peak times, stopping at certain stations only to allow for faster journeys.
On June 1, 2018 Chilean President Sebastián Piñera announced in the public account the extension of Line 4 to the sector of Bajos de Mena in Puente Alto that will be operational in 2026.
In October 2019, as a result of the protests caused by the rise in the subway fare, major damage occurred throughout the metro network. Line 4 was the most heavily damaged line out of all the metro's services. The Los Quillayes, San José de la Estrella, Macul, Protectora de la Infancia, Trinidad and Elisa Correa stations were completely burned; the latter two stations suffered the worst amount of damage to their structures and tracks, which would prevent normal operation of Line 4 for a period lasting 10 to 12 months. Line 4 partially reopened between Tobalaba and Quilín stations on October 28.
On November 6, the electrification of the tracks in the section between the stations Las Torres and Plaza de Puente Alto was restored, which suffered considerable damage, while evaluating the repairs to the line. On November 15, 2019, it was announced that service on the entirety of Line 4 would resume (with the exception of Vicuña Mackenna, Vicente Valdés, Hospital Sótero del Río, Las Mercedes and Plaza de Puente Alto stations) from November 18. On August 12, 2020, the Macul station was reopened. On September 14, the Elisa Correa, Los Quillayes and San José de la Estrella stations were reopened. Finally, on September 25, the Trinidad and Protectora de la Infancia stations were reopened, thus completing 100% operation at all stations.
Future
There is an expansion project planned for Line 4 proposing to extend the line to the north through Kennedy Avenue, benefitting the neighbourhoods of Las Condes and Vitacura and allowing an easier access to shopping centres located in Kennedy Avenue. Another proposal is considering connecting the Huechuraba business district with Tobalaba station, passing under the Costanera Center and San Cristóbal Hill.
The skip-stop express service[2] works during peak hours and allows trains to stop at alternate stations, reducing the number of stops and the duration of journeys. The stations on the line are divided into “green route” stations, “red route” stations and “common” stations (Spanish: estación común), where all trains stop and allow passengers to switch between red and green routes. The express service works from Monday to Friday, between 6am - 9am, 12pm - 3pm and 6pm - 9pm.
Note: in this wikitable a "Province" column is also added, as the Line 4 is the only Line to leave the Santiago Province, with five stations in the Cordillera Province.
