Travel
The CO₂ emissions from trains were found by multiplying the number of miles travelled in an average month by the emission factor of 0.10 kg per passenger mile and then by 12 (as there are twelve months in a year). This provided the individual CO₂ for one year.[1]

It was assumed that buses were urban diesel and an emission factor of 0.30 kg per passenger mile was used. The emission factor was multiplied by the miles travelled per week, and in turn this was multiplied by 52 to give an individual carbon dioxide emission for a year.[2]

www.vcacarfueldata.org.uk/downloads had an database of 2673 cars which included a section on CO₂ g/km for diesel and petrol cars, which ranged from 120-450 g/km . Average emission values for different categories of popular cars were used and in turn multiplied by the person's annual driven kilometres and divided by the number of people in the household (as Carbon Calculator provides a personal carbon footprint).

It has to be noted, however, that emission data for older cars could not be obtained due to the change in law in relation to carbon dioxide emissions and tax bands - data is unavailable.

The calculation for carbon emissions for aircraft used many assumptions. The emissions were calculated from fuel data and distance travelled.

The equation for the combustion of kerosene is 2C₁₃H₂₈ + 40O₂ =>26CO₂ + 28H₂O and it was assumed that the cruising distance = distance travelled - 250 miles. The cruising fuel = cruising distance * 10.1. Landing and take off fuel = 7840kg. The occupancy of an aeroplane is 80%. The aeroplane was a Boeing 747. Number of passengers = 370 * occupancy. And fuel per passenger = ((cruise fuel + take off and landing fuel) * single or return) / passengers.

The CO₂ emissions = fuel per passenger * 3 * (44/12) * (156/184).

The calculator used to find the distances between cities used the great circle distance principle. For more information, click here. [3]

_{References
[1] The emission factor was provided by Safe Climate and was in turn provided by Rail track which gave annual passenger miles and tonnes of CO2.
[2] The emission factor was provided by Safe Climate and was in turn provided by Bureau of Transportation, National Transportation Stastics for 2000.
[3] Distance calculator adapted from http://www.wcrl.ars.usda.gov/cec/java/lat-long.htm.}