would open on 25 November 2005, and the last in the series of extensions opened on 22 December 2005, with a total cost of US$170 million and a 27-million passenger increase annually. On November 30, 2005, the first underground leg of Line 4 from Tobalaba to Grecia, and the viaduct between Vicente Valdés and Plaza de Puente Alto opened to the public. The unfinished track from Grecia and Vicente Valdés was covered by a rail replacement bus service operated by Transantiago until March 2, 2006, when the remaining stations and track were finished. Line 4 at this time was the longest of the network, with an extension of and 22 stations serving Providencia, Las Condes, Ñuñoa, La Reina, Peñalolén, Macul, La Florida and Puente Alto. This new line also saw the introduction of new rolling stock, the AS-2002, manufactured by Alstom in Brazil, featuring more interior space than those running other lines. Finally, Line 4 would be complemented with the opening of a branch service on August 16, 2006, Line 4A, which connected Line 2 from La Cisterna with Line 4 at Vicuña Mackenna, running through the Américo Vespucio ring road. On May 26, 2016, Metro announced the extension of Lines 2 and 3, adding 8.9 kilometers and 7 new stations to the Metro network. Both extensions are expected to begin operations during the second half of 2021. The extension of Line 2 to the south will add 5.1 kilometers and 4 new stations connecting the current terminal station in La Cisterna with San Bernardo locality. The new terminal station will be located next to a hospital called Hospital El Pino in San Bernardo. Meanwhile, the extension of Line 3 to the west will add 3.8 kilometers and 3 new stations to the Metro network, connecting future station Los Libertadores with Quilicura. On November 2, 2017, Line 6 was inaugurated from Cerrillos to Los Leones adding 10 new stations. This new line does not have staffed ticket offices; instead there are automatic machines for ticket sales and loading money onto bip! cards. It has platform-edge doors to protect passengers, and traction power is supplied by overhead line equipment, not by conductor rails as on the other lines. It has new entrance and exit turnstiles at stations. The trains on Line 6 only have steel wheels, and are driverless. On January 22, 2019, Line 3 was inaugurated, after 9 years of