… something long and painted on a highway

DOUBLEYELLOWLINE

This road marking often separates lanes and signals no passing in some areas.

This clue hints at a common road marking that's long and painted on highways. The answer "DOUBLEYELLOWLINE" refers to the two parallel yellow lines often seen in the center of roads, indicating no passing. The wordplay is straightforward, describing the physical appearance and purpose of the marking. It’s a familiar sight for drivers, making the answer easy to recognize once you think about highway features.