I'm not sure if this poster was ever produced, as the LOC files it under "proposed poster".
The somewhat cryptic note on the LOC website also says that, "Effective group riding only begins with the swapping of rides. As more and more cars are not available for use in the future, the necessity for this transportation". As we all know, more and more cars are certainly available for use today, in the future, but ride swapping is still a good idea. Remember this poster was drawn up before HOV lanes, when people were glad to carpool, excuse me, ride swap, because not doing so used resources that the government thought it could better use to fight the war.
[Source: Library of Congress]