- Summary
Despite perceptions to the contrary, there is little difference in greenhouse gas emissions between cars and public transport. On a per passenger mile basis, cars emit nearly the same GHGs per passenger mile as all public transport outside the New York urban area. Hybrid automobile technologies are already producing GHG emissions lower than the New York public transport figure.
Demographia has posted greenhouse gas (GHG) emission data for US public transport by mode and for personal mobility mechanisms (cars and SUVs). The data is for 2005 and is calculated using US Department of Transportation, US Department of Energy and US Environmental Protection Agency data.
The results may be surprising to any who have assumed that public transport is inherently less GHG intensive than cars.
The average 2006 car emits 307 grams of GHG per passenger mile in urban driving. This is approximately 30 percent more than the average for public transport (233 grams).
Virtually all of the public transport advantage is due to the New York urban area, where 133 GHG grams are emitted per passenger mile, 57 percent less than the average 2006 car.
Outside New York, public transport and the average 2006 car emit have similar GHG emissions --- cars 307 and public transport 303.
Cars are becoming more fuel efficient, which is indicated by the hybrid and hybrid diesel data. Toyota’s Prius emits 147 GHG grams per passenger mile in urban driving, 10 percent more than the New York public transport figure of 133 grams. Hybrid diesel cars just entering the European market emit 101 GHG grams per passenger mile, 22 percent less than public transport in New York.
SUV’s are considerably more GHG intensive than both cars and public transport, emitting 443 GHG grams per passenger mile.
These estimates include the GHG emissions from electricity consumption and fuel refining. A full life-cycle analysis would be preferable, which would include GHG emissions from construction of public transport and highway systems, construction of vehicles, extraction of fuel for electricity generation and refining, disposal of vehicles and other materials, vehicle maintenance and administrative support.
