Road signs can be grouped into several categories: regulatory signs, warning signs and guide signs. Regulatory signs remind motorist of driving regulations, warning sign alert motorist to road conditions ahead and guide signs display destinations, distance and directions.
Road signs come in may different background colors that work as subtle visual cues to motorist: black and white for speeds, blue for services, brown for recreational or cultural sites, green for sign-postings, orange for construction, red for prohibition and yellow for warnings.
Circles road signs are exclusive to railroad signs, while octagons are designated for stop signs, and pentagon are used for advance school warnings and county route signs.
Triangular signs are generally reserved for the designation of yield and no-passing signs.
Trapezoidal signs are used to indicate recreational and national forest areas. Diamond-shaped signs are used for warnings. Vertical rectangular signs are reserved for regulatory signs, while their horizontal counterparts are used for guide signs, some warning signs and temporary traffic signs.
Cross-buck signs are used to indicate railroad crossings, while signs of unspecified shapes are generally used as router markers.
