Passenger numbers in 2015 beat historical records for the line, which has been largely attributed to the newer rolling stock and refurbished stations.

In 1978 a restructuring of the San Martín line was carried out by the de facto Military Government, so the terminus was set in Pilar, Buenos Aires Province.

With the privatisation of the entire rail network led in the early 1990s by President Carlos Menem, Ferrocarriles Argentinos ceased to operate metropolitan services.

The project also included a new maintenance yard, new tracks for the entire line with all level road crossings to be eliminated and replaced with bridges and tunnels.

Both governments cited benefits such as the improvement of road traffic and rail frequencies as reasons for building the 4.9 km (3.0 mi) viaduct.

[18] The section from Retiro to Villa del Parque (set as provisional terminus while works were in progress) was closed in 2018,[19][20] as a new viaduct (with an extension of 5 km) was being installed between intermediate stations Palermo and La Paternal to eliminate 11 level crossings in the city.

[25][26] The branch had been built and opened by the Buenos Aires Western Railway in 1908, connecting the San Martín, Roca and Sarmiento lines.

[29] By 1987, these plans were revisited and Ferrocarriles Argentinos signed a contract with the Soviet company Tecnostroyexport to use 25 kV AC railway electrification like that recently installed on the Roca Line, with the difference that electric locomotives would be used to pull the existing carriages instead of purchasing new Japanese Electric Multiple Units like on the Roca Line.

The collapse of the Soviet Union and economic problems in Argentina slowed the plans down and the privatisation of the railways in 1993 ultimately led to its cancellation.

[31] The national government announced in September 2015 that China Railway Construction Corporation was carrying out a feasibility study to assess the electrification of the line.

[32] A month earlier, the Ministry of the Interior and Transport had announced the possibility of financing the line's electrification through the Inter-American Development Bank.