Traffic sound is a term used to describe the various noises that are heard when vehicles are in motion. The most common traffic sounds include BEEP, TOOT, HORN, and HONK, all of which are four letter words. BEEP is usually associated with the sound of a car HORN or reversing vehicle, while TOOT is a more lighthearted sound often made by a car HORN. HORN is a loud, deep sound that is typically used to alert other drivers of an approaching vehicle. Finally, HONK is a sharp, loud sound that is usually made by a car HORN.