The Tren Suburbano () is an electric suburban rail system in Mexico City. It is operated by Ferrocarriles Suburbanos with concessioned trains from Construcciones y Auxiliar de Ferrocarriles (CAF). It was designed to complement the extensive Mexico City metro system, Latin America's largest and busiest urban rail network. The railway has one operative line with a length of with seven stations, located in Cuauhtémoc and Azcapotzalco in Mexico City, and Tlalnepantla, Tultitlán and Cuautitlán, in the State of Mexico. A second line is under construction to connect with the Felipe Ángeles International Airport (AIFA) in Zumpango. Additional expansions were proposed in the 2000s with a total length of of rail system. History and description Line 1 covers a route measuring from Mexico City's Buenavista Station to the State of Mexico's Cuautitlán. The section, which began commercial service on June 2, 2008 (after three weeks of fare-free trial operation), cost US$706 million to build, with the Mexican Federal Government contributing 55% of this investment. The inaugural demonstration trip of the service from Buenavista to Lechería Station and back again was made by then-President of Mexico, Felipe Calderón Hinojosa, and then-Governor of the State of Mexico (and eventual president of the country), Enrique Peña Nieto, with Calderón acting as the train's engineer. Line 1 was built on an existing at-grade railroad right of way. However, inside Mexico City itself on the approach to Buenavista Station, a considerable amount of grade separation, including below-grade excavation and new bridges, was necessary due to high density and traffic congestion. The construction elicited complaints by Mexico City residents who objected to having their neighborhoods split by the rail line, but the public supported the project overall. In addition to the track, the construction of Tren Suburbano also benefited from like-new electrification infrastructure already in place along most of the route, part of National Railways of Mexico (NdeM)'s Mexico City-Querétaro 25 kV 60 Hz mainline electrification completed in the 1990s but de-energized a few years later after NdeM was privatized. On August 24, 2005, Construcciones y Auxiliar de Ferrocarriles, S.A. (CAF) obtained a 30-year concession to supply rolling stock, build and operate the Tren Suburbano. The trains used on this service are electric trains built by CAF and are similar to the series 2000 trains of the Companhia Paulista de Trens Metropolitanos of São Paulo, Brazil. Service Ridership Line 1 was projected to carry 100 million passengers