NORTH BAY -- A round of Sonoma County freeway improvements are on track for completion in November, starting with the opening of a new five-mile, high-occupancy vehicle lane in each direction between Pepper Road in Cotati and Rohnert Park Expressway.

Known as the “Central A Project,” the $65.4 million Caltrans project broke ground in April 2010. A second “Central B Project” is also expected for completion in November, which will extend HOV lanes from Pepper Road to directly south of the Old Redwood Highway bridge.

When a third project, the $40 million “Wilfred Avenue Interchange Project,” is completed in late 2012 or early 2013, drivers will experience “a solid, unbroken HOV lane from Windsor to Old Redwood Highway,” said Bob Haus, spokesman for Caltrans District Four.

In addition to the new carpool lanes, Central A also involves the construction of new sound walls along the highway, replacement of the interchange between Highways 101 and 116 and work on the Sierra and Railroad Avenue undercrossings. A total of $29.6 million of the funding came from Proposition  1B bonds, $31.3 million from state funds and $4.5 million from Sonoma County's Measure M.

The Central B Project, at a cost of $16.3 million, will add a new sound wall  north of the Redwood Highway off-ramp, and the Willow Creek overcrossing will be widened. Construction on the Central B portion began in July of this year. Proposition 1B funds paid for the entire project.

Crews will be holding off on the final part of the paving, a rubberized asphalt, until next year, Mr. Haus said. Made from a mixture that includes recycled tires, the asphalt adds to the road’s durability but is not essential before drivers begin using the lane, Mr. Haus said.

The Wilfred project involves a 1.6-mile stretch of Highway 101 surrounding Wilfred Avenue in Rohnert Park, adding an HOV lane in both directions and an underpass that will simplify travel between the east and west parts of the city. On and off ramps in the area will also be widened.   

Some work in Marin County is also nearing completion, including an approximately $20 million Caltrans project restoring the highway surface between North San Pedro Road and Highway 37.

Expected to finish before 2012, the work involves so-called "Open-Grated Asphalt Concrete," a material that drains water and suppresses noise more effectively than traditional asphalt, said Dianne Steinhauser, executive director of the Transportation Authority of Marin. The OGAP treatment will also use rubberized asphalt.

"You know when you're on OGAP, because a lot of the (rain) spray is gone," she said.

The first phase of the Marin Sonoma Narrows Project, which will add HOV lanes on 101 between Highway 37 and Atherton Avenue, broke ground in July and is expected to last two years. Of the $50 million dollars allocated for the phase, $31 million came from Prop. 1B bonds.

At completion, the southbound HOV lane will only run between Rowland Avenue and Highway 37. After allocating funds to the rebuilding of interchanges and elimination of direct-to-freeway driveways in the Redwood Landfill and Redwood Boulevard area, planners only had funding left for the limited stretch. The southbound stretch is less congested, Ms. Steinhauser said.

Construction for the new interchanges will begin next year. When all phases of the Narrows project are complete, HOV lanes are expected to extend between Novato and Petaluma.