Environment & Science

CO2 and you: How transportation choices affect greenhouse gas emissions

File: Dirty tailpipe
File: Dirty tailpipe
Guy Frankland/Flickr Creative Commons

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With President Trump’s decision Thursday to withdraw from the Paris climate agreement — and California Gov. Jerry Brown’s vow to keep standards up in our state — you may be wondering what, if anything, you can do to help avert climate change.

One answer: the individual decisions we make about transportation on a daily basis, and the bigger decisions we make about transportation policies as society, can really add up.

The exhaust spewed by cars, buses, trains, planes and ships is the biggest source of greenhouse gas emissions in California. Of those, passenger cars contribute the most: 70 percent of transportation emissions, according to a report from the California Environmental Protection Agency.

California EPA

Data crunched by the Federal Transit Administration show that driving alone — by far the most preferred transportation mode — is the most polluting. The average car generates almost a pound of carbon dioxide per passenger mile.

The share of commuters driving alone has been on the rise in L.A. County in recent years. About 73 percent of L.A. drivers go solo, about 10 percent carpool and 7 percent use transit, according to Caltrans.

Federal Transit Administration

Taking public transit cuts that by about half, with heavy rail, like subways, being the most efficient option. That's followed by light rail, then bus.

It should be noted the average emissions listed for buses in the FTA analysis are likely based at least partially on a diesel bus fleet. The Los Angeles County Metropolitan Transportation Authority operates a clean-fuel fleet of mostly compressed natural gas buses.

The agency will decide this summer whether to move toward more electric buses as it prepares to buy dozens of new vehicles. Electric vehicles emit no emissions from their tailpipes — but they do utilize electricity, thus generating some greenhouse gases.

The U.S. Environmental Protection Agency estimated greenhouse gas emissions for a plug-in electric passenger vehicle operating in L.A. County is 100 grams of CO2 per mile.

Walking or biking are, of course, carbon-free options — that is, if you don’t reward yourself with a juicy steak dinner. That could produce about the same amount of CO2 as driving 30 miles, according to a study published last year.