American Union of Concerned Scientists, December 2008.
Note: Color-coded ranking are based on the distribution of CO2 emissions across modes. The analysis assumes typical car and typical SUV fuel economies of 23 mpg and 18 mpg, respectively. Train emissions reflect an average of electric and diesel operations. The analysis assumes use of turboprops for 100- mile flights, regional jets for 500-mile flights, and narrow-body jets for 1,000-mile flights, based on information from the Federal Aviation Administration.
