Welcome to Caltrans District 4

101 Widening Between Petaluma and Rohnert Park

This Project Has Been Completed

U.S. Route 101 Widening in Sonoma County - Central A Project

The “Central A Project” will widen a five-mile stretch of U.S. Route 101 in Sonoma County, from just north of Pepper Road in Cotati to Rohnert Park Expressway. Caltrans will build one new lane in each direction. The new lanes will function as High-Occupancy Vehicle (HOV) lanes, commonly known as “diamond lanes” or “car-pool lanes.”

In addition to the new lanes, the project will also provide new sound walls along the highway; will widen existing bridges at Copeland Creek, Laguna de Santa Rosa Creek; and will replace the interchange of Highways 101 and 116 and the Sierra Avenue and Railroad Avenue undercrossings.

Caltrans broke ground on the $55 million project in April, 2010. Work is expected to finish in the Summer of 2012.

This stretch of U.S. Route 101 is the latest in a series of widening projects in Sonoma County. Two years ago, a segment of 101 in Santa Rosa was also widened. When all segments are complete, there will be a continuous HOV lane through the most densely populated section of Sonoma County, offering commuters a viable alternative to solo commuting.

Central “B” Project

The Central “B” Project will extend the HOV lanes from Pepper Road to just south of the Old Redwood Hwy bridge. In addition, crews will build a new soundwall on southbound 101 just north of the Redwood Highway off ramp, and will widen the existing Willow Brook Creek Overcrossing.

Construction began in July of 2011 and is expected to finish in Summer 2012.
Construction Photos photos
Project Map Map