Under Section 2121 of the California Streets and Highways Code, every county is required to certify their maintained mileage to the State annually in May. In turn, the State is required to certify public maintained road mileage to the FHWA by June 1.

Due to the construction of new county streets in subdivisions, the installation of authorized gates, road abandonments, and the use of more accurate measuring devices, the number of road miles maintained by the Yolo County Department of Community Services, Public Works Division, has historically fluctuated over time.  Public Works staff periodically updates the County’s maintained mileage database to account for these changes. Not included in the total maintained road mileage are state highways and unmaintained roads within County right of way.  

On May 9, 2023, the Board of Supervisors certified the 2022 maintained mileage as 751.778 miles. Due to corrections made in calendar year 2023 to the maintained mileage database, 752.225 miles of roadways will be reported as the 2023 certified maintained mileage for Yolo County. 

Maintained mileage is a factor in a variety of apportionment formulas used to distribute federal and state funds. At the federal level, federal-aid lane miles are used to apportion state shares of the National Highway System Program, the Surface Transportation Program, and the Highway Safety Improvement Program. In turn, the State makes portions of these program funds available to the County via either formula or competitive grant processes.

The federal government uses a classification system for all roads based on traffic volumes, degree of access and uninterrupted speed over certain distances. Classifications range from “Local” for low usage local access roads, to “Arterials” for the highest usage with longer distances of uninterrupted speeds and some degree of access control. Yolo County has only 116.334 miles of paved roads that are classified as Other Principal Arterial, Minor Arterial, or Major Collector and are eligible for federal funds (15% of the total maintained miles).

The Sacramento Area Council of Governments (SACOG) also uses the maintained mileage data, along with traffic volume information supplied in the state’s Highway Performance Monitoring System (HPMS) reports, to determine conformity with air quality regulations.