giving the metro network at that point a total of , 154 stations and 10 lines. Sixth stage (1994–2000) Assessment for line B began in late 1993. Line B was intended as a second línea alimentadora for northeastern municipalities in the State of Mexico, but, unlike line A, it used pneumatic traction. Construction of the subterranean track between Buenavista (named after the old Buenavista train station) and Garibaldi began in October 1994. Line B was opened to the public in two stages: from Buenavista to Villa de Aragón on 15 December 1999, and from Villa de Aragón to Ciudad Azteca on 30 November 2000. Seventh stage (2008–2014) Plans for a new STC Metro line started in 2008, although previous surveys and assessments were made as early as 2000. Line 12's first service stage was planned for completion in late 2009 with the creation of track connecting Axomulco, a planned new transfer station for Line 8 (between Escuadrón 201 and Atlalilco) to Tláhuac. The second stage, connecting Mixcoac to Tláhuac, was to be completed in 2010. Construction of Line 12 started in 2008, assuring it would be opened by 2011. Nevertheless, completion was delayed until 2012. Free test rides were offered to the public in some stations, and the line was fully operational on 30 October 2012. With minor changes, Line 12 runs from Mixcoac to Tláhuac, serving southern Mexico City for the first time. At long, it is the longest line in the system. Line 12 differs from previous lines in several aspects: no hawkers are allowed, either inside the train or inside the stations; it is the first numbered line to use steel railway tracks; one must have a Tarjeta DF smart card to access any station since Metro tickets are no longer accepted. In the book Los hombres del Metro, the original planning of Line 12 is described; although it was to begin at Mixcoac as it does today, Atlalilco and Constitución de 1917 stations of Line 8 were to be part of Line 12. The same map shows that Line 8 would have reached the Villa Coapa area and that it would not have had a terminal at Garibaldi, but at Indios Verdes, linking with Line 3. In addition, the book shows that Line 7 would have terminated at San Jerónimo. None of these plans have been confirmed by the Mexico City government. In 2015, mayor Miguel