International Energy Agency: “ GHG intensity of passenger transit modes, 2019.”
1 The effect of different modes of travel on the climate can be measured in “grams of carbon dioxide-equivalent per passenger-kilometer” (gCO2-eq/pkm), or how much CO2 and other greenhouse gases a single passenger puts in the atmosphere for every kilometer they travel. According to the International Energy Agency, cars emit between 57 and 322 gCO2-eq/pkm—compared to buses at just 22-92 gCO2-eq/pkm, and trains at 6-118 gCO2-eq/pkm. International Energy Agency: “ GHG intensity of passenger transit modes, 2019.”