|
|
| Fig. 1:TGV Trainset 16 on display on track H at Gare de Lyon. (Image Source: Wikimedia Commons) |
The Paris to Lyon corridor, spanning approximately 455 kilometers [1], is one of the busiest and most important intercity routes in France. Although air travel is available, the relatively short distance makes flying less time- and cost-efficient. In contrast, the TGV high-speed train (Fig. 1) has emerged as an alternative, offering a faster, convenient, and low-carbon solution. This report aims to estimate the annual reduction in carbon dioxide (CO2) emissions resulting from passengers choosing the TGV over short-haul flights between Paris and Lyon, thereby quantifying the environmental benefits of this modal shift from air travel to high-speed rail.
According to data determined by the French Ministry for an Ecological and Solidary Transition, the CO2- equivalent emission intensity of TGV high-speed rail is 3.37 g CO2/passenger/km. [1] For air travel, we conservatively assume a large short-haul aircraft (e.g., Airbus A321), which produces a lower emission intensity (117 g CO2/passenger/km) compared to a smaller aircraft. [1] Using a one-way route length of 455 km, the avoided CO2 emission per traveler is therefore:
| (117 g passenger-1 km-1 - 3.37 g passenger-1 km-1) × 455 km | |
| = | 51,701.65 g⋅passenger-1 |
| = | 51.7 kg⋅passenger-1 |
The annual number of passengers traveling by TGV between Paris (Paris Gare de Lyon station) and Lyon (Lyon Part-Dieu station) is not directly available. However, a lower bound can be derived based on three assumptions:
A passenger's origin and destination are independent; that is, for a passenger departing from Paris, the probability of arriving in Lyon equals the share of all passengers whose destination is Lyon Part-Dieu, and vice versa.
For each station, half of the reported passenger volume represents departures and the other half represents arrivals.
Travel-segment choice is independent of rail service type; accordingly, the proportion of Paris-Lyon passengers among all TGV users is assumed to match their proportion within the overall passenger population.
Based on data reported by SNCF (the French National Railway Company), SNCF Group operators transport approximately 15 million passengers per day, corresponding to 5,475 million passengers annually. [2] Among this total, Paris Gare de Lyon records 141 million passengers per year, while Lyon Part-Dieu records 53 million. Applying assumptions (1) and (2), the estimated fraction of travelers whose origin is Paris Gare de Lyon and whose destination is Lyon Part-Dieu is
| fP→L | = | 141 2 × 5475 |
× | 53 2 × 5475 |
= | 6.23 × 10-5 |
Similarly, the fraction of travelers whose origin is Lyon Part-Dieu and whose destination is Paris Gare de Lyon is
| fL→P | = | 53 2 × 5475 |
× | 141 2 × 5475 |
= | 6.23 × 10-5 |
Thus, the total estimated proportion of Paris-Lyon passengers in the overall passenger population is
Applying assumption (3), the estimated number of Paris-Lyon passengers using TGV services is obtained by multiplying the previously calculated share by the total annual TGV traffic (126 million passengers in 2024) [2]:
The yearly CO2 reduction lower bound is then
This estimate is highly conservative, as the Paris-Lyon corridor is one of the most popular and heavily served high- speed rail routes in France, making assumption (1) unlikely to hold in practice. However, the exact passenger count for this specific city-pair is not publicly available, so this approach provides the most cautious lower-bound estimate given the available data.
If assumption (1) is relaxed and it is instead assumed that 20% of travelers departing from Paris Gare de Lyon terminate at Lyon Part- Dieu, and vice versa, then the resulting estimated proportion of Paris-Lyon passengers within the overall TGV passenger population becomes
| fL→P + fP→L | = | 0.2 × ( | 141 2 × 5475 |
+ | 53 2 × 5475 |
) | = | 3.54 × 10-3 | ||||
The corresponding annual CO2 reduction is therefore
| 126 × 106 passengers × 3.54 × 10-3 × 51.7 kg passenger-1 | = | 2.306 × 107 kg | = | 23,060 tonnes |
If assumption (3) is also set aside and a 5% share of TGV passengers is assumed to travel on the Paris-Lyon segment, reflecting the prominence of this route, the annual reduction becomes
| 126 × 106 passengers × 0.05 × 51.7 kg passenger-1 | = | 3.257 × 108 kg | = | 325,710 tonnes |
From these results, it is clear that the exact annual reduction depends on the model used to estimate the number of travelers. However, one conclusion is certain: for each passenger, choosing the TGV train instead of a short-haul flight results in a (117-3.37)/117 ≈ 0.971 (97.1%) CO2 reduction, which shows that the high-speed train is a significantly more climate-friendly option while offering comparable travel time (approximately 2 hours).
We have discussed the TGV high-speed rail as a fast, convenient, and markedly low-carbon mode of travel on the Paris-Lyon corridor. Per-passenger comparison shows that substituting a TGV trip for a short-haul flight reduces CO2 emissions by 97.1%, reflecting the substantial difference in emission intensity between the two modes. Since the exact number of passengers traveling between Paris and Lyon by TGV is not publicly reported, several assumptions were used to construct estimates. Under the most conservative set of assumptions, the annual CO2 reduction attributable to TGV travel on this corridor is approximately 814 tonnes. If more realistic assumptions about passenger distribution are adopted, such as a 20% Paris-Lyon pairing rate or a 5% TGV market share on this segment, the annual reduction increases to tens to hundreds of thousands of tonnes.
Across all scenarios, the conclusion remains robust: shifting travelers from short-haul aviation to high-speed rail yields substantial environmental benefits. On the Paris-Lyon corridor, the TGV delivers these benefits while maintaining comparable door-to-door travel times, making it an environmentally advantageous alternative without sacrificing convenience or efficiency.
© Yuxuan Wu. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "GHG Information For Transport Services," Governemt of France, Ministry For an Ecological and Solidary Transition, France, Jun 2019.
[2] "Sustainable Mobility, Sustainable Planet," SNCF Groupe, 2025.
