If you take the train instead of flying, you will almost certainly have a far lower carbon footprint for that journey. The emissions gap between rail and aviation is one of the larger and more consistent findings in transport research — though the exact figures vary by route, country, load factor and how you account for indirect climate effects. Here is what the evidence actually shows, stated as carefully as the evidence warrants.
Why rail is so much lower-carbon than flying
The difference is structural. Aircraft burn kerosene — a fossil fuel — to generate lift and thrust. There is no clean alternative at scale, and the physics of flight mean that a large amount of energy is required for every kilometre travelled. Trains, by contrast, run on electricity in much of Europe, and Europe's electricity grid has been steadily decarbonising. Even where trains run on diesel, the energy required per passenger-kilometre is substantially lower than for aviation.
Several factors drive the gap:
- Energy efficiency. Trains move more passengers per unit of energy than aircraft, particularly at typical European distances.
- Electricity vs kerosene. Where trains run on renewable or low-carbon electricity — as in France (largely nuclear), Scandinavia (largely hydro) and increasingly elsewhere — operational emissions fall dramatically.
- Non-CO₂ effects at altitude. Aircraft emit not just CO₂ but also nitrogen oxides and water vapour at cruising altitude, which have additional warming effects. The science here is more uncertain than for CO₂ alone, but most researchers believe the total climate impact of aviation is higher than CO₂ emissions alone suggest. Trains produce no high-altitude effects.
What the ballpark figures look like
Research bodies and government agencies that study transport emissions consistently find that rail produces a small fraction of the CO₂ per passenger-kilometre that aviation does. Depending on the study, the methodology and the specific route, train emissions tend to be roughly five to twenty times lower than flying for the same journey. Some studies on routes where trains run on very clean electricity find even larger gaps; routes where trains run mainly on diesel show a smaller (but still meaningful) difference.
A useful frame rather than a precise number: taking the train instead of flying a typical European route of 1,000 km is often described as saving somewhere in the range of 80–90% of the flight's CO₂ — though exact figures vary by route, operator and year. The key point is the order of magnitude, not the decimal place.
We are deliberately not quoting specific kilograms per passenger-kilometre here, because those figures vary significantly between sources, methodologies and years. Numbers cited in one study may use different assumptions about load factors, infrastructure emissions, or electricity grid carbon intensity than another. If you want to compare specific routes, the European Environment Agency and individual national transport agencies publish emissions factors, and the International Energy Agency tracks transport sector data.
Why the exact numbers are genuinely uncertain
Emissions comparisons between modes are harder to make precisely than they first appear. The complications include:
- Load factor. A full train is much lower-carbon per seat than a near-empty one. The same applies to aircraft. Emissions per passenger depend on how many other passengers are sharing the journey.
- Electricity source. A French TGV running on nuclear electricity has very different lifecycle emissions from a diesel-hauled train in a country with a coal-heavy grid.
- Route distance and speed. Short-haul flights are disproportionately carbon-intensive because take-off and landing use far more fuel than cruising. Rail has no equivalent penalty for short distances.
- Non-CO₂ forcing. Whether and how to include the non-CO₂ warming effects of aviation is contested in the research literature. Including them increases the apparent gap; excluding them reduces it.
- Infrastructure emissions. Some analyses include the carbon cost of building and maintaining the transport infrastructure; most do not, because it is very hard to allocate fairly.
None of this uncertainty undermines the main conclusion — rail is substantially lower-carbon than flying — but it does mean any single precise figure should be treated with scepticism unless you can trace it back to its methodology.
Which routes show the biggest difference
Short to medium European routes show the most dramatic contrast, partly because the train is genuinely competitive on time and the flight is shortest-haul (and therefore disproportionately fuel-intensive per kilometre). Paris to London, London to Brussels, Paris to Amsterdam, Frankfurt to Munich — these are journeys where the train is already the faster or comparable option door-to-door, and where the carbon saving is also very large.
For longer routes — say London to Istanbul or Paris to Tokyo — the emissions case becomes more complicated, partly because no continuous rail alternative exists for the full distance, and partly because the train journey takes several days rather than hours.
The carbon cost of not travelling at all
It is worth noting that the comparison between train and plane assumes the journey will happen. For some travellers, the right question is whether to take the trip at all. But if the journey is going to happen — for work, to see family, for a holiday — then surface travel is almost always the substantially lower-carbon choice for European distances.
Practical implications
If reducing your transport carbon footprint matters to you, the most effective single action is replacing one or more short-haul flights per year with surface travel. Our guide to travelling without flying covers how to plan and book this in practice. The guide to Europe without flying shows how far you can reach by train.
Night trains — covered in our night trains guide — are a particularly effective substitution: they replace both a flight and a hotel night, and they run on electricity across most of Europe.
Frequently asked questions
Is the train always lower-carbon than flying?
For almost all European routes, yes, rail is substantially lower-carbon per passenger-kilometre than aviation. The gap is largest where trains run on low-carbon electricity. The only realistic exceptions would involve very unusual circumstances such as an empty diesel train versus a packed, very efficient aircraft — not a realistic comparison for scheduled services.
Should I include non-CO₂ effects when comparing?
Many researchers recommend it, because aviation's non-CO₂ effects at altitude are believed to add meaningful warming beyond the CO₂ alone. Doing so makes aviation look even more carbon-intensive relative to rail. However, the science is more uncertain than for CO₂ itself, and different organisations handle it differently. The European Environment Agency and the Intergovernmental Panel on Climate Change both discuss this in their transport publications.
Does a rail pass change the carbon equation?
No — the emissions per journey depend on the train, not on how you bought your ticket. A seat on a TGV produces roughly the same emissions whether you paid with a pass reservation or a point-to-point ticket.
What about carbon offsetting for flights?
Offsetting is contested: the quality of offset schemes varies enormously, and many researchers argue that reducing emissions at source is preferable to compensating elsewhere. Replacing a flight with a train eliminates most of the transport emissions rather than attempting to balance them.
Sources and further reading:
- Transport sector emissions data: European Environment Agency, International Energy Agency.
- Non-CO₂ aviation effects: Intergovernmental Panel on Climate Change (IPCC) aviation chapter.
- Rail emissions factors by country: individual national transport agencies and the European Commission.