METHOD
-OLOGY
General
All emissions are calculated in SI units (International System of Units) of CO2 and CO2 equivalent.
Aviation
The flight route distance is calculated using great circle distance between each airport on the route, plus a standard factor to account for extra distance of approach and landing at each airport. The range of possible equipment (plane) types that operate on each flight route is known. The user may specify the exact type of equipment that was/is used or, if not known, the average for all equipment on this route is used. Emissions are then calculated based on the ICAO Carbon Calculator (United Civil Aviation Organization) - fully implemented and used as the base model. Fuel production/distribution factors are accounted for as well as high-altitude effects - for that we use the Chalmers University Travel and Climate methodology report (Jörgen Larsson and Anneli Kamb). So while the ICAO calculator provides a base level of accuracy for the raw CO2 emissions, it’s too lenient and doesn’t take into account extended factors which the Chalmers report does. However the Chalmers report uses a uniform base model which is generally accurate if averaged over many users but not accurate for individual flights. Also the Chalmers calculator doesn’t seem to correctly take into account the actual flight routes - it just uses a great circle distance between the start and final end locations. In summary, Eco Trip is more accurate for individual flights and flight routes than the Travel and Climate calculator and it also accounts for production/distribution and high altitude effects, improving on the ICAO calculator.
General road transport
Road types and country-specific speed limits are taken into account to better model fuel efficiency. Acceleration/deceleration for junctions is modelled and this can show a marked difference between urban and motorway driving, for example, leading to greatly improved accuracy when compared to more simplistic methods. Passenger factors for public transport can generally be specified or an average used. For car journeys, car occupancy can be specified.
ICE Cars
Calculations are derived from driving distance, fuel type and engine efficiency. Fuel production/distribution factors are then added using the Chalmers report methodology.
EV Cars
CO2 emissions from the various power sources for electricity production of each country and/or US State on the driving route are taken into account. These are then multiplied by the exact distance driven through each region.
Public Transport
Buses follow the same methodology as diesel or electric cars, with average emissions per passenger calculated. Average capacity of the bus is taken into account, or can be specified by the user.
Trains use similar methodology as diesel or electric cars, with average emissions per passenger calculated. Average electrification of the countries rail network is taken into account, or if known the exact fuel type can be specified (electric / diesel).
Other transport types, will be added in the future including:
Ferries
Trams
Subway
Trains
