Even if you can't do it today, plan a car-free day in the near future and try out some alternate modes of transport—or spend the day at home.

Honor World Carfree Day by finding another way to get around.

RODALE NEWS, EMMAUS, PA—September 22 has been designated "World Carfree Day," a day when drivers around the world are supposed to park their cars and look for transportation alternatives that pollute less, use fewer nonrenewable resources, and possibly boost heart rates. Based on numbers from the Department of Transportation, Americans are already driving about 3 percent less than they were a year ago, most likely due to last July's skyrocketing $4-a-gallon gas prices. But car-free days have never quite taken off in the U.S. they way they have in Europe, says Sara Stout, spokesperson for the World Carfree Network, which sponsors Carfree Day.

So whether you leave the car in the garage today, or pick a "car-free" day on the weekend when it's more convenient, here are some transportation alternatives that will spare you a day's gas, plus keep you healthy and the air cleaner:

#1: Public transit
This one is probably fairly obvious, but to celebrate World Carfree Day, many local public transit agencies, such as the one in Chapel Hill, NC, provide free passes for the day. Look up your local bus system and see if you can get a free ride.

#2: Rollerblades
According to the safety advocacy group Surface Transportation Policy Project, 25 percent of car trips that Americans take are less than one mile, and around 60 percent are less than five miles. If you're too hurried to walk that mile, strap on some in-line skates. An easy Rollerblading pace is about 8 miles per hour; you could travel a mile in 7.5 minutes at that pace compared with one mile in 15 minutes at a moderate-to-brisk pace. If you're going five miles or more, though, you're better off biking. Remember your helmet and elbow and knee pads when Rollerblading, and visit the Inline Skating Resource Center for beginner's classes and instructors in your area.