Have you ever wondered what it would be like to give up your car for one day? How about what it would be like to give up your car for one day in Los Angeles? Could you do it for seven days?

That's exactly what two actors from ABC's crime series "Castle" decided to try with The Alternative Travel Project. For seven days over the course of one month, Seamus Dever and Stana Katic traded sitting in their cars in bumper-to-bumper L.A. traffic for moving with their own two feet. They biked, took the bus and walked their way around a city not known for its public transportation system.

It may have required more planning than just picking up their car keys from the kitchen counter, but they were rewarded with more exercise, more money not spent on gas and a greater appreciation for their city. Two less cars on the road, even for seven days, put that much less carbon emissions into the already smog-filled L.A. sky.

The Alternative Travel Project shows that even in a car-centric place such as Los Angeles, cars are still a choice rather than a necessity. Dever's and Katic's journeys were documented in four short episodes that can be found on The Alternative Travel Project website. You can also pledge to go carless for a day on the website and send in photos of your new alternative travel adventures.