County roads in Ohio comprise 29,088 center line miles (46,813 km), making up 24% of the state's public roadways as of April 2015. Ohio state law delegates the maintenance and designation of these county roads to the boards of commissioners and highway departments of its 88 counties. Each county has distinct construction, signage, and naming practices for the roads under its jurisdiction. Within each county, townships maintain separate township road networks under the advice of the county engineer. Each board of county commissioners certifies the total county- and township-maintained mileage within its county. The Ohio Department of Transportation catalogues these certifications on an annual basis.