The 2026 factors
| Mode | kg CO2e per passenger km |
|---|---|
| Domestic flight, average passenger, with radiative forcing | 0.22928 |
| Short-haul flight (UK to Europe), average passenger, with radiative forcing | 0.12786 |
| Average car, one person, fuel unknown | 0.16591 |
| National rail | 0.03092 |
| International rail (Eurostar) | 0.01135 |
The international rail factor is low because it is based on Eurostar's electricity use on the UK side of the route, reported through the Office of Rail and Road and converted with the UK grid factor. The flight factors include the extra warming that planes cause at altitude: see our post on radiative forcing. Neither row includes well-to-tank emissions, which add to both.
Common routes, return trip, one traveller
| Route | Distance (km, return) | Fly (kg CO2e) | Train (kg CO2e) | Flying is |
|---|---|---|---|---|
| London to Edinburgh (National rail) | 1,068 | 245 | 33 | 7× higher |
| London to Glasgow (National rail) | 1,110 | 255 | 34 | 7× higher |
| London to Paris (Eurostar) | 694 | 89 | 8 | 11× higher |
| London to Brussels (Eurostar) | 700 | 90 | 8 | 11× higher |
| London to Amsterdam (Eurostar) | 741 | 95 | 8 | 11× higher |
Distances are the straight-line, or great circle, distance between Heathrow and the destination airport. The government's flight factors already include an 8% uplift for indirect routes and delays, so that is the distance to use. We've used the same distance for the train to keep it simple. A rail route is rarely a straight line, so this flatters the train slightly, but even if every rail journey here were 7 times as long, it would still be lower. Driving alone to Edinburgh and back in an average car would be about 177 kg, between the two.
A worked example
A firm sends 4 people to a client in Edinburgh 2 times a year. Flying, that is 4 × 2 × 245 = 1.96 tonnes CO2e a year. By train it is 0.26 tonnes, a saving of 1.69 tonnes. If each trip needed an extra hotel night for everyone, that would add 83 kg, a small fraction of the saving.
Turning it into a travel policy
- Rail first for UK trips and the Eurostar network. A simple rule is "train for any journey under a set number of hours", with exceptions agreed by a manager.
- Economy when you do fly. On short-haul and long-haul flights, premium seats take up more room in the plane, so the government's business and first class factors are higher than economy.
- Ask whether the trip is needed at all. See video calls instead of travel.
- Record the policy in your plan. Business travel is Scope 3 category 6, one of the categories a PPN 006 Carbon Reduction Plan must include, so a rail-first policy is a reduction measure with a number attached.
How Carbon Recycling helps
Record flights by entering the airport codes and Carbon Recycling works out the distance, picks domestic, short-haul or long-haul, and applies the 2026 factor with radiative forcing. Rail journeys go in as passenger km, national or international, and hotel nights by country. Everything lands in Scope 3 category 6, so you can see how much a rail-first policy cuts, and add it to your Carbon Reduction Plan as a measure. For the other side of travel, see switching company cars to electric.