A hybrid car.
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Driving less

In the U.S., more than 30 percent of CO₂ emissions comes from transportation, mostly from personal cars and trucks. Each gallon of gasoline saved keeps 9 kilograms (20 pounds) of CO₂ out of the air.

Various measures that one can take to drive less include:

• Walking

• Biking - In Copenhagen, Denmark, 36 percent of the population commutes to work by bike, saving 90,000 tons of CO2 emissions per year compared to driving the same distance by car.

• Carpooling

• Combining errands

• Taking mass transit - By riding public transportation instead of driving a car, one person saves on average 2.2 metric tons of CO₂ per year.

Driving fuel-efficient cars

A hybrid driven 24,000 kilometers (15,000 miles) a year that gets 19 km/liter (45 mpg) emits about 4.0 metric tons of CO₂ each year. An SUV that gets 8.5 km/liter (20 mpg) emits 10.3 metric tons of CO₂ each year.

Maintaining your car

Inflating tires

Soft tires waste gas--enough to emit an extra 113 kilograms (250 pounds) of CO₂ per car each year.

Changing filters

Clean air filters save 360 kilograms (800 pounds) of CO₂ emissions per year.

Driving efficiently

Better driving habits mean better fuel economy and fewer CO₂ emissions. Every mile an hour over 60 lowers fuel economy by about 1 percent.

Using cruise control on the highway

Avoiding quick starts and stops

Aggressive highway driving can lower fuel economy by about 30 percent.

Staying within the speed limit

Idling less

Idling burns gas, and every gallon burned emits about 9 kilograms (20 pounds) of CO₂. Plus, idling gets zero miles per gallon.

Traveling light

Carrying an extra 45 kilograms (100 pounds) of cargo can cut mileage by 2 percent.

Flying less

Every gallon of jet fuel burned emits 9.5 kilograms (21 pounds) of CO₂. An average flight from New York to Washington emits about 80 kilograms (176 pounds) of CO₂ per passenger.

Avoiding overpacking

Extra weight means more fuel burned and more emissions.

Taking direct flights when possible

Idling, circling, takeoffs and landings burn a big chunk of fuel on any flight.

Using other types of transportation

Electric commuter trains emit about 25 percent less CO₂ per passenger-mile compared to airplanes.