When you log a journey and tell us how you would otherwise have made that journey (if you hadn’t been taking part in the challenge), we compare the two modes of transport to find the difference in CO2 emissions for each journey. This number gives you your total CO2 savings so far during the challenge. The smaller number at the bottom of the box indicates how much CO2 you have saved when compared with someone travelling by car – if all of your logged journeys would have otherwise been by car, these figures will be the same.
Calculations are based on data from the Defra document “2010 Guidelines to Defra / DECC’s GHG Conversion Factors for Company Reporting: Methodology Paper for Emission Factors” and use approximate figures based on the average car.