Sonoma County continues to have the worst roads of any county in the Bay Area, according to a new report.

Half of the 2,378 miles of roads in Sonoma County and its nine cities are in poor condition or failing, according to the report from the Metropolitan Transportation Commission. Only 21 percent were rated excellent or very good, the lowest in the region.

The problem is concentrated in the unincorporated parts of Sonoma County, where almost two-thirds of the 1,379 miles of road are poor or failing.

Petaluma's roads ranked fifth from the bottom among the 100 cities and nine counties surveyed in the annual report, which was released last week.

County officials have struggled to maintain an aging road network that was largely built before new paving technology created more durable roads. Sonoma County roads have ranked at the bottom of the Bay Area's nine counties since 2001, when the MTC began compiling the Pavement Condition Index.

Tom O'Kane, deputy director of the Sonoma County Public Works Department, said officials will release a 20-year plan to deal with road rehabilitation sometime early next year. The plan will look at various options for additional revenue, he said, including a sales tax measure on a future ballot.

"This is long-term neglect," he said. "It goes back decades. It's going to take a long-term effort to get all the roads back into shape."

Officials are also considering creating a transportation district that could raise revenue for road maintenance by assessing properties, O'Kane said. Revenue from a statewide gasoline tax that is used for road repair has been flat because motorists are driving less, fuel efficiency has improved and sales of hybrid and electric vehicles has increased.

The pavement condition index does not take into account recent improvements by the county to 67 miles of roads, about 5 percent of the total, O'Kane said.

The survey results are not surprising, said Craig Harrison, founder of Save Our Sonoma Roads, which lobbies for more funding for roads. He said the county has deferred major road repairs for years because of budget constraints.

Harrison pointed out that the survey gave residential county roads a score of 34 out of 100, by far the worst in the Bay Area.

"That just glows in the dark as being horrible," he said.

Petaluma's 174 miles of roads are consistently ranked as the worst in the county. Public Works director Dan St. John blamed the lack of funding for road repairs on the dip in gasoline tax revenue.

"We know Petaluma's roads need work," he said. "Petaluma, like many agencies, is lacking in dedicated funding for pavement maintenance."

Cotati's roads were listed as "at-risk," meaning they need major rehabilitation work.

The survey labeled roads in Healdsburg, Sebastopol, Santa Rosa, Cloverdale and Rohnert Park as "fair." Windsor and Sonoma have the best roads in the county, according to the survey.

St. Helena and Larkspur have the worst roads in the Bay Area. The best roads are in the Contra Costa community of Brentwood.

You can reach Staff Writer Matt Brown at 521-5206 or matt.brown@pressdemocrat.com.