A back-seat game
While driving or riding, people inside the car look for examples of the next letter of the alphabet. Somebody sees a 'LANE ENDS' sign, and calls out, "A, LANE!"
Any example of the letter that is not attached or inside the players' car is fair game.
Variations include: selecting the person who must find the next letter, can't call two letters from the same sign, running the alphabet backwards.
Then there's the ever-popular, "if we can't find Q within two miles, we're skipping it!"