For over a decade, France’s Grenelle II environmental law has required transport providers to disclose the amount of CO₂ emitted for each journey. This requirement has a dual purpose: make transport players aware of their carbon impact, and encourage travellers to choose cleaner mobility options.

We report emissions for each journey—expressed in CO₂ equivalent (CO₂e)—whenever a customer searches for a journey. We updated these values in August 2024 based on the input database for 2023.

To calculate the carbon footprint for a journey, we multiply the distance travelled by the average amount of CO2e emitted per passenger per kilometre, based on the type of train—TGV INOUI, OUIGO, INTERCITÉS, TER or Transilien.

For example, if a passenger travels from Strasbourg to Versailles on a TGV and a Transilien commuter train, the formula is:

Distance travelled with TGV INOUI x GHG emissions per kilometre for a TGV INOUI passenger + Distance travelled with Transilien x GHG emissions per kilometre for a Transilien

We take the distance from a database of railway lines in kilometres. For each type of train, we calculate average annual emissions by multiplying energy consumption for the preceding year by the CO₂e emission factor for each type of energy, and dividing the result by the number of passengers carried that year and the distance they travelled.

This method covers only the “energy use” portion of our CO₂e footprint--the carbon impact of the traction energy consumed by the train. To provide comprehensive emissions data for SNCF mobility solutions, we took part in a working group led by Ademe, France’s Agency for Ecological Transition, on the impact of manufacturing our vehicles. We also joined a study by the consulting firm Carbone 4 on including the carbon impact of both manufacturing and maintenance, plus consumption by our maintenance centres.