This is a comparison between the pollution created by the use of a bus to that of a car. For the Volkswagen Jetta the diesel version puts out between 3.7 and 7.4 times the pollution (except for carbon dioxide, which technically isn't a pollutant) of the gasoline powered one. This would mean the diesel Jetta would have to carry as much as 7 times the passengers of the gasoline powered Jetta for the emissions to be equivalent. I would assume a diesel powered bus also puts out a lot of pollution. So this investigation looks at what the passenger loads of a diesel bus have to be in order for it to have an emission reduction over a gas powered passenger car.