In plotting out an upcoming trip from D.C. to Boston I was pleased to discover Greyhound's new, greener bus fleet which in addition to sporting free wifi and AC plugs (bloggers, put your hands up) boasts a super fuel efficient engine. According to Greyhound calculations, the per-passenger mile works out to approximately 1/3 less CO2 emissions than a hybrid car taking the same trip.
Comparing the Greyhound trip with a Prius the 438 miles trip works out to...
PRIUS: 438 mi / 45 mpg avg. = 9.73 gallons x 20 lbs CO2/gal (that is the conservative estimate) = 195 lbs CO2
GREYHOUND (according to their calcs): = 195/3 = 65 lbs CO2
Then I wondered how that compares to a typical commuter airplane flight on, say the JetBlue's nonstop commuter flight (flight mileage is 401 miles)...
FLIGHT (according to CarbonFund calculator): = .08 tons x 2000 lbs = 160 lbs CO2
Note: the airline calculation does not incorporate "radiative forcing," or the increased impact of CO2 emitted at high altitudes. If you factor that in it works out to .21 tons (or 420 pounds).
The greyhound wins this carbon race.