Which of the following is NOT a purpose of highway road signs?

Highway road signs serve several essential purposes designed to enhance safety and facilitate the smooth operation of traffic. One of the primary purposes is to provide travel information, such as directions or distances to destinations. Another crucial function is regulating traffic flow, which involves signs that indicate speed limits or the arrangement of lanes for safe travel. Furthermore, highway signs inform motorists about various regulations that must be followed to ensure safety on the roads, like "Stop" or "Yield" signs.

Advertising local attractions, while it may seem relevant for drivers, is not one of the primary functions of highway road signs. These signs focus on traffic management and safety rather than promoting specific businesses or tourism opportunities. Therefore, recognizing that road signs are meant primarily for information, regulation, and guidance rather than advertising helps clarify why the correct answer identifies advertising local attractions as not a true purpose of highway road signs.