Flying vs. Driving: Which Is Better for the Environment?

Driving in a relatively fuel-efficient car (25–30 miles per gallon) usually generates fewer greenhouse-gas emissions than flying. In assessing the global warming impact of a trip from Philadelphia to Boston (about 300 miles), the environmental news website Grist.org calculates that driving would generate about 104 kilograms of carbon dioxide (CO2)—a leading greenhouse gas—per typical medium-sized car (regardless of the number of passengers) while flying on a commercial jet would produce some 184 kilograms of CO2 per passenger.

Carpooling Generates the Fewest Greenhouse Gases

While even driving alone would be better from the standpoint of greenhouse-gas emissions, carpooling makes the most environmental sense. Four people sharing a car would collectively be responsible for emitting only 104 kilograms of CO2, while the same four people taking up four seats on a plane would generate some 736 kilograms of carbon dioxide.

Cross-Country Calculations Show Stark Contrasts

Journalist Pablo Päster of Salon.com extends the comparison further, to a cross-country trip, and comes to similar conclusions. Differences in the numbers are attributable to the use of slightly varying assumptions regarding fuel usage and source equations. Flying from San Francisco to Boston, for example, would generate some 1,300 kilograms of greenhouse gases per passenger each way, while driving would account for only 930 kilograms per vehicle. Again, although even driving alone has a lower carbon footprint than flying, sharing the drive with one or more people would lower each individual’s carbon footprint accordingly.

Air Travel Is Economical for Long Distances

Just because driving might be greener than flying doesn’t mean it always makes the most sense. It would cost far more in fuel to drive clear across the United States in a car than to fly nonstop coast-to-coast. That’s not even factoring in the time spent in restaurants and hotels along the way. Those interested in figuring out driving fuel costs can consult the American Automobile Association's nifty online Fuel Cost Calculator, where you can enter your starting city and destination as well as the year, make, and model of your car to get an accurate estimate of what it will cost to “fill ‘er up” between points A and B.

Carbon Offsets Can Balance Travel-Related Emissions

Once you’ve made your decision whether to drive or fly, consider purchasing carbon offsets for renewable energy development to balance out the emissions you are generating. TerraPass, among others, is a company that makes it easy to calculate your carbon footprint based on how much you drive and fly, and then will sell you offsets accordingly. Monies generated through carbon offsets fund alternative energy and other projects, such as wind farms, that will ultimately take a bite out of or eliminate greenhouse-gas emissions. TerraPass will also calculate your home energy consumption.

Public Transportation Beats Both Car and Air Travel

Of course, an individual’s emissions from riding a bus (the ultimate carpool) or a train would be significantly lower. Päster adds that a cross-country train trip would generate about half the greenhouse-gas emissions of driving a car. The only way to travel greener might be to bicycle or walk—but the trip is long enough as it is.

Edited by Frederic Beaudry

EarthTalk is a regular feature of E/The Environmental Magazine. Selected EarthTalk columns are reprinted on DotDash Environmental Issues by permission of the editors of E.