The number of Californians walking, biking and using public transportation has more than doubled since 2000. 

In the study, done by the California Household Travel Survey, nearly 23 percent of household trips were made without the car, compared to 11 percent in 2000.

From avoiding traffic to looking for parking spots, Mark Dinger with Caltrans says a variety of reasons could explain why the numbers are rising.

"It might also reflect the changing California lifestyle too. People are into doing healthy things, and that means more walking -- and biking, too," he said. 

The study covers the traveling behavior of about 42,000 in 58 counties.