[2] The line of tram-train Évry – Massy finds its origin in the project of Tangential the South or Tangential Southwest, which suggested connecting by a new RER line the city of Versailles, even that of Achères in Yvelines, to that from Melun in Seine-et-Marne, including Massy and Évry.

In February 2008 the projected timescale was established as follows: Within the framework of the "Plan Banlieue" approved by the interministerial committee of the cities on 20 June 2008, the State claimed to be ready to finance at the level of 220 million euros "to support at least 4 specific projects of which the Tramway Line 4 towards Clichy-Montfermeil, the Tangentielle Nord, the Massy-Evry tram-train and the connection RER D/RER B (Barreau de Gonesse)".

The public inquiry of the first phase, that is approximately 20 km (12 mi) connecting the multimodal pole of Évry-Courcouronnes Centre with the station of Massy-Palaiseau, was held from 7 January to 11 February 2013, within the various municipalities concerned by the project.

Work began at the beginning of 2017, then the validation of the protocol of financing on 9 March 2017 by the regional elected representatives guaranteed the pursuit of the project for the deadlines, with an opening planned in 2020.

At the end of 2008, the SNCF proposed that the section between Versailles-Chantiers and Pont de Rungis (when it will be merged, thanks to the putting into service of the streetcar-train Évry-Massy in 2017) will be integrated into a project of tram-train connecting the stations of Versailles-Chantiers and Sucy-Bonneuil and it will replace the RER C (since December 2023 replaced by Transilien Line V on this segment).

On 26 January 2011 the State and the Region agreed on the broad guidelines for public transport in Île-de-France by quoting the possible extension of the Évry-Massy tram-train to Versailles-Chantiers with the indication of a putting into service planned for 2020.

The tram-train would completely replace the C8 branch of the RER C. The project was presented in preliminary dialogue from 1 June to 7 July 2013.

Then, in an urban tramway network, it will serve the municipalities of Épinay-sur-Orge, Morsang-sur-Orge, Viry-Châtillon, Grigny, Ris-Orangis, Courcouronnes and finally Évry.