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Hwy 101 Greenbrae/Twin Cities Corridor Improvements

The Transportation Authority of Marin has actively engaged project stakeholders to collectively develop a series of multi-modal improvements that increase the operational efficiency and safety of the Highway 101 Greenbrae/ Twin Cities Corridor for all users, including motorist, bicyclists, pedestrians and transit riders.  Funding is provided from the Regional Measure 2 Program, a $1.00 increase in bridge tolls on bay area bridges approved by voters in 2004.    

Recent Actions - Updated October 4, 2013

At the September 26, 2013, the TAM Board provided a recommendation to consider a set of alternative projects to be pursued further. This recommendation will be forwarded to the Metropolitan Transportation Commission for a future action as the intended use of Regional Measure 2 funds in the Richmond San Rafael Bridge Corridor.  

View Staff Report

View list of recommended projects 



Greenbrae Corridor Advisory Working Group

A Greenbrae Corridor Advisory Working Group has been formed to explore a range of options and strives to agree on a recommendation for the Greenbrae Corridor Improvement Project.  Click here to view TAM's calendar

Draft Environmental Document

TAM, in partnership with the lead agency Caltrans, is please to announce the release of the Draft Environmental Document for the Highway 101 Greenbrae/Twin Cities Corridor Improvement Project in compliance with the National Environmental Policy Act (NEPA) and the California Environmental Quality Act (CEQA).  The Initial Study (with Proposed Mitigated Negative Declaration)/ Environmental Assessment is available for review at the Transportation Authority of Marin's office located at 781 Lincoln Avenue, Suite 160, San Rafael CA 94901

The document is presented on this project web page and has been broken down into smaller files that can be downloaded for review. Please be patient while the files download.  You will see a white screen until file fully loads.


0        Cover Pages_Table of Contents  (0.2MB)
1        Intro_Purpose and Need_Project Description_Permits  (5.4MB)
2        Issues with No Effect_Land Use (Part 1)  (7.4MB)
3        Land Use (Part 2)_Growth_Community Impacts (Part 1)  (9.0MB)
4       Community Impacts (Part 2)_Utilities_Traffic_Visual (Part 1)  (10.7MB)
5       Visual (Part 2)  (9.8MB)
6       Visual (Part 3)  (7.2MB)
7       Visual (Part 4)  (11.8MB)
8       Visual (Part 5)_Cultural Resources  (5.7MB)
9       Hydrology_Water Quality_Geo_Paleo_Hazmat_Air Quality_Noise (Part 1)  (7.6MB)
10     Noise (Part 2)  (9.4MB)
11     Noise (Part 3)  (0.4MB)
12     Natural Communities_Wetlands_Plants_Animals_Threatened_Endangered_Invasive (0.5MB)
13     Cumulative Impacts_Climate Change (1.6MB) 
14     Comments and Coordination_Preparers_Distribution  (0.2MB) 
15     Appendices (12MB)

Technical Studies

1      Visual Impact Assessment Report (5.5MB)
2      Air Quality (4.1 MB)
3      Natural Environment Study (NES) (6.5MB)
4      NES Appendices B-H (4.2MB)
5      NES Wetland Delineation 1 (1.4MB)
6      NES Wetland Delineation 2 (8.8MB)
7      NES Wetland Delineation 3 (6.1MB)
8      Paleontology (0.8MB)
9      Hazardous Material Phase 1 (5.0MB)
10    Hazardous Materials Appendices (8.0MB)
11    Hazardous Materials Addendum (7.1MB)
12    Location Hydraulic Study 3.1MB)
13    Water Quality (1.4MB)
14    Noise Study (1.4MB)
15    Community Impact Assessment (2.5MB)
16    Traffic Operations Report (TOR) (13.6MB)
17    TOR Appendices A-D (9.3MB)
18    TOR Appendices E-H (5.6MB)
19    Preliminary Geotechnical Report (0.5MB) 


TAM has prepared two animations of the proposed improvements within the corridor.  One view is a "fly-thru" perspective and the other view is from a driver's perspective traveling along the highway.  Both animations can be viewed using the following web links: 

Fly-Thru:           "

Driver's View:  


Previous Project Activities

AReview Multi-Modal Exhibit Board (7.7MB)


 Map  V2.jep



Project Study Report

On March 17, 2011 the Caltrans District Director approved the Project Study Report (PSR). The PSR is a document that defines the project scope, cost and schedule which is then used as the basis for developing the engineering design and environmental document. By reaching this significant milestone TAM, Caltrans and our surrounding stakeholders can now focus on developing and refining the proposed options that will ultimately improve the operations and safety of the roadway network, improve access and use of public transit and improve a network of pedestrian and bicycle facilities in the Greenbrae Corridor.

Read the Project Study Report. This report contains a number of lengthy attachments which are available for review at the TAM office. Contact the staff member listed below to schedule an appointment to review the attachments

 Public Open House and Scoping Meeting (September 2009)
The Transportation Authority of Marin, in cooperation with the Department of Transportation hosted an informational open house and scoping meeting on Tuesday September 29, 2009 to provide a project update on our recent progress and to announce the initiation of the environmental phase.  The event was well attended by over 120 interested stakeholders.  A series of stations were set up with display exhibit boards that presented and described the project development process.  TAM continues to work with the community to develop a suite of integrated multi-modal transportation improvements to improve mobility for all users within the corridor. The improvement options under consideration were on display for review and discussion.

Report from the TAM Board Meeting November 19, 2009
The TAM Board acknowledged recent comments received from the public, the Town of Corte Madera, and the City of Larkspur expressing concerns regarding the final phase of the proposed southbound improvement alternative. The Chair stated his appreciation for all affected parties to listen, participate and develop the best alternatives for all users of the corridor. The Board recognized areas of community consensus and the recent progress made to develop the multi-modal improvement alternatives. The Board also recognized areas of disagreement and recommended the limits of the project be modified to allow remaining improvements to be studied further. This direction effectively removes the proposed final phase of the southbound improvement option from further development and study. Favorable community consensus was expressed on the northbound improvement option (Option ā€œEā€) for further study. TAM and our partners will continue to work closely with Caltrans to advance the improvement options still under consideration as part of the environmental analysis.

View the staff report, presentation (1.6MB), or meeting minutes (Item No. 11) (2.4MB)from the November 19, 2009 Board Meeting.


Staff Contact:
Bill Whitney, P.E.
Phone:  (415) 226-0823



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Last updated: 10/4/2013 4:32:49 PM