The €320m project will be jointly funded by the state, the regions of Ile-de-France and Grand Est (Alsace-Champagne-Ardennes-Lorraine), and eight local councils.

The western section of the route between Paris Est and Gretz Armainvilliers is already electrified at 25kV 50Hz ac as part of the Paris suburban network. Paris - Troyes services, which are operated by B82500 AGC bi-mode multiple units, also run under electric power as far as Gretz, where they switch to diesel traction.

Extension of the wires to Troyes will involve the installation of 6000 catenary masts, 320km of catenary wire and 160km of signal cable. SNCF Network will rebuild or replace 41 of the line’s 68 overbridges to increase clearances for electrification. A new substation will also be required and the signalling centre at Romilly will be renewed.

Electrification on the Gretz - Nogent-sur-Seine section will be completed in 2021 and the remainder of the line to Troyes will be energised in 2022.