What is a common purpose of blue signs on highways?

Blue signs on highways primarily serve to display service information. This includes crucial details about facilities available to travelers, such as gas stations, rest areas, hospitals, hotels, and food options. The use of blue is standardized by traffic regulations to ensure that drivers can easily identify and access these essential services while on the road, promoting safety and convenience.

While blue signs do indicate various services, other colors and sign shapes are designated for different purposes. For instance, speed limits are indicated by white signs with black text, and directional signs to recreational areas typically use green. Warning signs for merge areas would also not use blue but rather a yellow background with specific symbols or wording to alert drivers to changes in traffic conditions.