During World War II, the government encouraged carpooling because they needed the gas and rubber for the war (source). Here is a sample of the propaganda:

This one is, as it appears, by Dr. Seuss:

The next two are from the State of Ohio:

In the comments, both Eoin and Toban B. (T.B.) pointed us to this poster (found here).

Lisa Wade, PhD is a Visiting Scholar at Tulane University. She is the author of American Hookup, a book about college sexual culture; a textbook about gender; and a forthcoming Introduction to Sociology text. You can follow her on Twitter, Facebook, and Instagram.