Transportation is a big deal when it comes to greenhouse gas emissions. All told, it makes up about 27% of climate-damaging emissions in the U.S., second only to electricity generation. Driving less, opting for public transportation, bicycling, or walking are all part of the solution.

But sometimes a car is the only reasonable way to get somewhere.  If that’s the case, think about sharing your ride. There are on-line services that can help you line up riding partners, whether you’re looking for a ride, or to offer a ride, whether you’re commuting to work, heading home from college, or driving across the country.

Many cities have their own commuter match-up programs, but Ridester.com is a nation-wide service that seems worth checking out. Zimride.com works with universities and corporations to create ride-sharing match-ups within existing communities. Check it out to see if your company or school is already on it. If not, maybe you can get them to sign up.

But this doesn’t need to be complicated.  With email and Facebook it’s very easy to put a note out to friends asking the simple question “Does anyone want  a ride to _____ (fill in the blank: book club, the school play, church, etc.)?” The simple act of asking is the first step toward saving a gallon, and saving some carbon dioxide emissions. And it comes with the side-benefit of getting to know people just a little better, which is definitely good for the planet.