Travel emissions explained
A number becomes useful when you can follow the calculation.
Distance, traveller count and the emission factor determine the result. A meaningful comparison also needs compatible routes, occupancy assumptions and accounting boundaries.
Editorial review
This page explains Farleda’s current planning calculation. The interactive example is not an available connection, travel recommendation or measurement of a completed journey.
Farleda · Editorial review
Distinguish passenger-km from vehicle-km.
A rail or flight factor per passenger-kilometre already incorporates occupancy from its underlying model. Multiply it by the traveller count to obtain the group total. The car factor is per vehicle-kilometre: Farleda assumes one vehicle for up to four travellers and rounds vehicle count up.
- Rail/flight: kilometres × g CO₂e per passenger-km × travellers ÷ 1,000.
- Car: kilometres × g CO₂e per vehicle-km × rounded-up vehicle count ÷ 1,000.
- Per-person result: group emissions ÷ traveller count. A larger group does not automatically reduce the total.
Use each mode’s own distance for real alternatives.
The example below holds distance constant across modes to make the units visible. An actual comparison needs separate rail, road and flight distances and an explicit treatment of access legs. A great-circle distance between airports is not the entire door-to-door journey.
Worked example · model v1.1
Change the assumptions. Understand the difference.
The same distance for each mode, static factors and no access legs. This isolates the calculation; it does not represent an actual journey.
| Mode / factor | Group | Per person |
|---|---|---|
| Rail · catalogue31 g CO₂e/pkm | 18.6 | 9.3 |
| Short-haul flight · incl. RF128 g CO₂e/pkm | 76.8 | 38.4 |
| Car · one vehicle per 4 people166 g CO₂e/vehicle-km | 49.8 | 24.9 |
300 km · 2 travellers · 1 vehicle
Source: Farleda factor catalogue v1.1. Planning proxy, not a full life-cycle assessment. Factor sources and boundaries are documented in the methodology.
Read the accounting boundary alongside the number.
The current catalogue uses rounded DESNZ 2026 factors as a disclosed planning proxy. The national-rail row is not a measurement of every European train. The electric-rail grid model is a separate calculation using an assumption of 0.09 kWh per passenger-kilometre.
- Flight factors include the stated radiative-forcing uplift.
- Upstream energy emissions are not fully added in the current catalogue; this is not a complete life-cycle assessment.
- Displayed factor ranges describe scenarios or classes, not statistical confidence intervals.
A modelled difference still needs impact evidence.
The gap between two model values first establishes the difference between those scenarios. Whether someone would have flown, took a train instead and caused a particular environmental outcome needs additional evidence. A Farleda passport signs a stated planning and calculation record; the signature alone does not prove completed travel.
Common questions
Why can a full car look lower per person?
The vehicle total is shared between more people. Distance, vehicle type, actual occupancy and accounting boundaries still matter; the example uses an average factor.
Are these measured values for my connection?
No. The example uses Farleda’s static catalogue. Suitable operator data may fit a specific case better and needs its own source and accounting-boundary review.
Where is the full methodology?
The methodology page explains factors, routing, the grid model and passport boundaries. The data inventory lists sources, while the technical note covers ranking and the evaluation plan.
