Highway 101 Congestion Relief Program

Printable Map

Highway 101 through most of Sonoma County was constructed between 1954-1962. It is the primary north – south corridor through the county.  A 1958 traffic count at the College Avenue interchange indicated that 15,000 cars a day were using the freeway (at that segment). A 2006 Caltrans traffic count at the same location found that over 125,000 cars a day were traveling on the same four-lane freeway. Planners in the 1950's envisioned a freeway widened to six lanes in the 1970s to handle projected population growth in Sonoma County. However, as the population grew, the improvements lagged severely behind.

It is a goal of the SCTA to create a safe, convenient, free flowing Highway 101 with a less intense rush hour period where traffic moves at a steady pace. To reach this goal, SCTA developed a program of six Highway 101 HOV projects that would not only create a continuous HOV lane from the Sonoma County line to Windsor, but would also address operational and safety problems throughout the corridor.  A separate environmental document for each HOV project has either been certified or is in development.

The following projects are part of the Sonoma County Transportation Authority’s 2004 Comprehensive Transportation Plan and are included in the Highway 101 Congestion Relief Program for Sonoma County. These projects will improve traffic operations and provide continuous High Occupancy Vehicle (HOV) lanes between southern Marin County and Windsor in Sonoma County.

1.  South Santa Rosa (Santa Rosa Avenue to Highway 12)
The first phases of this project have been constructed and approximately 4.6 miles of HOV lanes in each direction are open to traffic in southern Santa Rosa. Landscaping is scheduled for late 2007 through 2008.  Ramp metering will be implemented as a separate contract, once adjacent projects are complete.  The environmental document for this project can be found at:
http://www.dot.ca.gov/dist4/sonoma101/SON101.html

2) Downtown Santa Rosa (Highway 12 to Steele Lane)
This project will add approximately 2.5 miles of HOV lanes in each direction. Ramp improvements and auxiliary lanes will also be provided to encourage HOV use and improve mainline traffic operations.  The project also includes new structures; structure replacement and improvements; sound wall construction; intelligent transportation systems, including ramp metering; and modification to the surrounding local street network to improve local circulation and access. Construction of the first two  phases began in March 2006 with completion estimated in 2009.  Subsequent phases to construct the local street access and landscaping is partially funded and expected to begin as early as 2009. The Caltrans website for this project is located at:
http://www.dot.ca.gov/dist4/son101/

The environmental document for this project can be found at:
http://www.dot.ca.gov/dist4/son101/101hovdocuments.htm

3. Wilfred (Rohnert Park Expressway to Santa Rosa Avenue)
This project will add approximately 1.6 miles of HOV lanes in each direction; add auxiliary lanes between the Rohnert Park Expressway and Wilfred Avenue Interchanges; add a southbound collector/distributor between Santa Rosa Avenue and Wilfred Avenue; provide ramp improvements; expand an existing park-and-ride lot; add intelligent transportation systems, including ramp metering; and modify the local street network (including a direct connection from Golf Course Drive to Wilfred Avenue) to improve access and circulation. This project is fully funded with construction anticipated to begin in 2009.   The environmental document for this project can be found at:
http://www.dot.ca.gov/dist4/wilfredave.htm

4. North (Steele Lane to Windsor River Road)
This project will add approximately 7.5 miles of HOV lanes in each direction.  Ramp improvements, auxiliary lanes, and a southbound collector/distributor between Airport Boulevard and Fulton Road will also be provided to encourage HOV use and improve mainline operations.  The project also includes new structures; structure improvements; intelligent transportation systems, including ramp metering; and sound walls.  This project will be constructed in phases, with the first phase (Phase A) consisting of the HOV elements, some ramp improvements and existing pavement rehabilitation.  Subsequent phases will include a collector distributer between Airport Boulevard and Fulton Road, soundwalls, and landscaping.  Phase A is fully funded with construction anticipated to begin in 2009. The environmental document for this project can be found at:
http://www.dot.ca.gov/dist4/envdocs.htm

5. Central (Old Redwood Highway in Petaluma to Rohnert Park Expressway)
This project will add approximately 6.4 miles HOV lanes in each direction, ramp improvements, and auxiliary lanes. The project also includes new structures; structure improvements; intelligent transportation systems, including ramp metering; and soundwalls.  This project will be constructed in phases, with the first phase (Phase A) consisting of improvements in the northern 3.3 miles of the project limits (does this include to Pepper Road?. Phase A is fully funded with construction anticipated to begin in 2009. The environmental document for this project can be found at:
http://www.dot.ca.gov/dist4/envdocs.htm

6. Marin/Sonoma Narrows (MSN) (Highway 37 in Novato to Old Redwood Highway in Petaluma)
This project will add approximately 17 miles of HOV lanes in each direction.  The project also includes new structures; structure improvements; intelligent transportation systems, including ramp metering; and soundwalls.  The project would also upgrade the 9-mile long “Novato Narrows” section from expressway to freeway.  It would provide interchanges and frontage roads to replace eighty (80) at grade intersections and driveways, and would replace the San Antonio Creek Bridge, which is prone to flooding and major highway closures.  It would also improve horizontal and vertical alignment, in order to bring the facility to freeway standards.

This project will be constructed in phases.  The first 3 phases will include a portion of the new HOV lanes in the southern 4-mile section (Phase A-1) in Marin County, a new interchange at San Antonio Road (Phase B-1), and a new interchange at Petaluma Boulevard South (Phase B-2).  The first 3 phases are fully funded with construction anticipated to start in 2010 and 2011.  A phasing plan for subsequent phases is in development and will be dependent on future funding opportunities.  The draft environmental document can be found at:
http://www.dot.ca.gov/dist4/msn/

6-C-1.  East Washington (On-ramp Improvements)
Once a part of the Marin/Sonoma Narrows (MSN) project, the East Washington project has been separated to advance delivery.  This project will correct the ramp geometry of the southbound on-ramp.  It will also provide a new on-ramp from westbound East Washington Street to northbound Highway 101 in order to help local circulation in Petaluma.  The East Washington project is fully funded with construction anticipated to begin in 2009.  The draft environmental document will be released in mid-November 2007.