If you are familiar with the calculations of this prerequisite, you'll notice that you basically calculate the average CO2 equivalent of a commute trip (one-way) based on type of transport and distance, and then get a transportation score; very straight forward. But of you look closely on the table with CO2e pounds/mile for each mode, the difference between car solo and bus is not that much, about 26%. I ran the calculations for the project, and it seems that it will not comply with the prerequisite since most people travel by bus.
So, I did some research, and it seems that the value comes from the document "Updated Comparison of Energy Use & Emissions From Different Transportation Modes Oct.2008", which shows 308 gCO2/pass-mile for a transit bus. Then, I found a new version of the document "Updated Comparison of Energy Use & CO2 Emissions From Different Transportation Modes April 2014" which shows 136 CO2/pass-mile for a transit bus; considerably lower than the value from Oct.2008.
Does someone know if there is some error on the calculation from 2008? Any suggestions on how to proceed?