Kelley Blue Book, the vehicle-buying guide, recently surveyed Americans to gauge their attitudes toward autonomous cars. First, though, it had to tell them what an autonomous vehicle is.

Even as tech companies and auto makers make bold plans to put fully self-driving cars on the road within five years and the Obama administration rushes to craft regulations for such a future, the survey of more than 2,200 people found that consumers are rather clueless about it all. The results released Wednesday underscore challenges for...