A Policy on Geometric Design of Highways and Streets, 1990 by the American Association of State Highway and Transportation Officials. (also known as the "AASHTO Manual") is the commonly recognized resource and standard for road design standards most civil engineers dealing with roadway design. Through incorporation by reference in the Land Division Ordinance and the Public Road Improvement Ordinance, it is the County's basic road design standard. Local fire department access standards reflect the minimum road standard which have precedence over AASHTO standards where appropriate.