Signs may be categorized into one of three classifications. These classifications are regulatory signs, warning signs, and guide signs.
Regulatory Signs - Inform motorists of traffic laws or regulations. Includes intersection right-of-way (STOP, YIELD), speed control, movement control, parking, pedestrian, and some miscellaneous signs. Regulatory signs commonly use a black, red, or white legend on a black, red, or white background.
Warning Signs - Give notice of a situation that might not be readily apparent, including both roadway related and traffic related issues. Includes changes in alignment, intersections, advance warning of control devices, converging traffic lanes, narrow roadways, changes in highway design, grades, roadway surface conditions, railroad crossings, entrances and crossings, miscellaneous signs, as well as non-vehicular warning signs. Warning signs commonly use a black legend on a yellow or fluorescent yellow green background.
Guide Signs - Guide motorists along streets and highways. Includes route designations, destinations, emergency service signs, motorist service signs, public transportation signs, and general information signs. Guide signs commonly use a white legend on a green background.