How emissions are calculated
To calculate the average quantity of CO2 emitted per kilometre and per person, transport providers divide their energy consumption from the previous year (applying a CO2 emissions factor by energy type) by the number of passengers transported that year and the distance they travelled. An emissions factor is then obtained which will be used to calculate emissions for a specific trip, depending the distance of the trip and the mode of transport used.
The way a trip is calculated is important because it determines how the final CO2 emissions estimate is calculated. See how this distance is calculated according to the means of transport used:
- In public transport, the distance travelled is the sum of point-to-point distances between each step of your trip.
- When driving, the distance travelled is calculated as a point-to-point distance between the departure point and the arrival point.
In public transport, when a trip necessitates using several modes of transport with transfers, each portion is handled individually, then the CO2 emissions are added up. For example, for a train and metro trip, the estimate of CO2 emissions is the sum of the emissions from the train trip + those of the metro trip, calculated in the following way:
- Trip distance x CO2 emissions/km of a passenger for this mode of transport
Our calculator uses the following emissions levels per mode of transport (valid as of 1st January 2015), per person:
- by train on the Transilien network: 6.2 g/km
- by RER: 6,2g/km
- by tram: 3,7g/km
- by metro: 3,9g/km
- by bus: 101g/km
- by car: 161g/km
Walking and Vélib bicycle trips are not taken into account.