Q: Why did the girl spread peanut butter on the road?
A: To go with the traffic jam!
Explanation: Peanut butter and jelly is a common type of sandwich in the United States. Jam and jelly are synonyms (they are not identical but very much the same). A traffic jam is when there are so many cars in one place that the cars are stopped (or moving very slowly). This joke plays with the word jam- the kind that goes with peanut butter and the kind that stops traffic. Ha ha ha!