Travel impact
Methodology
Last updated July 08, 2026
Farfolk estimates travel impact from the trips you log. Each move from one city to the next becomes a travel segment, assigned to the year of the arrival city. If no transport mode is saved for a segment, Farfolk treats it as a flight.
These figures are estimates for personal context and comparison. They are not medical, environmental, tax, or regulatory advice.
Distance
Distance is calculated between the latitude and longitude of each consecutive city using the haversine formula. This gives a great-circle distance, which is a simple estimate of the shortest path over the Earth.
Real routes can be longer because of road networks, rail lines, ferry routes, airport routing, and layovers. Farfolk uses the same distance basis across modes so yearly totals remain consistent and easy to compare.
The “average” comparison uses approximately 3,900 km of flying per year as the US average.
CO2
CO2 is estimated by multiplying segment distance by a per-passenger, per-kilometer factor for the saved transport mode.
| Mode | Factor | Basis |
|---|---|---|
| Plane | 0.075 kg/km | ICAO CORSIA, economy class, direct combustion only |
| Ferry | 0.115 kg/km | UK government GHG conversion factors |
| Car | 0.170 kg/km | Solo driver in an average petrol car |
| Bus | 0.027 kg/km | Average coach |
| Train | 0.006 kg/km | EU average electric rail |
| Walk / bike | 0 | No direct travel emissions counted |
Flight CO2 excludes radiative forcing from contrails and high-altitude nitrogen oxides; including those effects would typically increase the climate-impact estimate. Car estimates assume solo occupancy, and train estimates vary materially by country grid mix.
The footprint comparison uses approximately 16,000 kg CO2 per year as the US average personal CO2 footprint.
Radiation
Radiation is estimated only for flight segments. Ground and sea transport are treated as negligible for this tracker.
Cosmic radiation at cruise altitude is approximated at 10 μSv per hour. At a typical cruise speed of 900 km/h, that works out to about 0.0114 μSv per km.
Actual exposure varies by route latitude, altitude, aircraft path, flight duration, and solar activity. For context, Farfolk compares annual flight exposure with the EPA recommendation to keep additional exposure below 1,000 μSv per year. A chest X-ray is commonly approximated as 20 μSv.
Sources considered include ICRP Publication 60 and FAA/CARI-style cosmic radiation methodology.