Orange County Transportation Authority

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  • SR-55 (I-405 to I-5)

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    Stay Informed

Overview Tab Content:

  • Notice of Intent to Adopt a Mitigated Negative Declaration, Notice of Availability of an Environmental Assessment, Announcement of Public Review Period Extension
  • OCTA, in cooperation with Caltrans, is proposing improvements to the segment of SR-55 between I-405 and I-5. The project is currently in the environmental phase.

    The Draft Environmental Document, also called the Proposed Mitigated Negative Declaration (MND) and Initial Study/Environmental Assessment (IS/EA) and other project documents are now available online at  and at several local libraries in the project area:

    • Caltrans District 12 Office, 3347 Michelson Drive, Suite 100, Irvine, CA 92612-1692
    • Orange County Transportation Authority, 550 South Main Street, Orange, CA 92868
    • Santa Ana Public Library, 26 Civic Center Plaza, Santa Ana, CA 92701
    • City of Irvine City Hall, 1 Civic Center Plaza, Irvine, CA 92606-5207
    • Tustin Library, 345 East Main Street, Tustin, CA 92780

    The Draft Environmental Document was released on Nov. 25, 2015, and is available for public review and comment until 5 p.m. Jan. 22, 2016.

    Comments must be submitted in writing to Caltrans by 5 p.m., Jan. 22, 2016. Send comments to:

    • Mail comments to:
      Charles Baker, Senior Environmental Planner
      California Department of Transportation, District 12, Environmental Analysis - Specialist Branch
      3347 Michelson Drive, Suite 100
      Irvine, CA 92612-1692
    • Or email comments to:

    More Information
    For more information on the SR-55 Improvement Project Public Meeting, contact Chris Boucly at 714-560-5326 or
    Si prefiere recibir información en español, por favor llame a Camilo Rocha al 714-730-2339.

    Project Need

    • Limited capacity during peak periods
    • Inadequate merging distances as a result of closely spaced on- and off-ramps
    • Non-standard lane and shoulder widths at some locations

    Project Overview

    Currently, the SR-55 freeway has a total of five lanes in each direction, including the carpool lane, and provides enhanced traffic flow to approximately 295,000 motorists traveling the freeway each day. The SR-55 serves thousands of locals and visitors alike as the main route to get to work, home, popular beach communities and entertainment venues. The proposed improvements will allow residents, businesses and motorists to see enhancements to the SR-55 corridor that will increase capacity, improve traffic operations and improve mobility and reduce congestion.

    Thanks to Measure M (Orange County’s half-cent transportation sales tax), $1.5 billion worth of improvements have been made to I-5 during the past 20 years. The Renewed Measure M (M2) Freeway program promises to earmark another $1 billion for SR-55 improvements in central and north Orange County.

Details Tab Content:

  • The existing configuration of SR-55 corridor includes four general purpose lanes and one continuous-access high-occupancy vehicle (HOV) lane in each direction. The SR-55 project proposes to reduce congestion and increase freeway capacity for an existing four-mile stretch of the SR-55 in both the northbound and southbound directions, between I-405 and I-5. OCTA and Caltrans currently are conducting an environmental study which proposes to add new lanes and improve mobility for commuters within Orange County. There are currently four “build” alternatives as well as one “no-build” alternative that are being prepared for project analysis.

    • No Build Alternative - The No Build Alternative keeps SR-55 in a status quo condition. This alternative includes no additional lanes or merging lanes. 
    • Alternative 1: Add Auxiliary Lanes in Each Direction between On- and Off-Ramps -Alternative 1 would add auxiliary lanes (or merging lanes) in each direction on SR-55 between on- and off-ramps.
    • Alternative 2: Add One General Purpose (GP) Lane in Each Direction - Alternative 2 would add one general purpose lane in each direction on SR-55 from McFadden Avenue to MacArthur Boulevard.
    • Alternative 3: Add Auxiliary Lanes between On- and Off-Ramps and One General Purpose Lane in Each Direction - Alternative 3 would add auxiliary lanes between on- and off-ramps and one general purpose lane in each direction of SR-55 freeway from McFadden Avenue to MacArthur Boulevard.
    • Alternative 4: Add Auxiliary Lanes between On- and Off-Ramps and one High-Occupancy Vehicle Lane - Alternative 4 would add auxiliary lanes between on- and off-ramps and one high occupancy vehicle lane in each direction from the northbound and southbound I-405 connector to the northbound I-5 connector.

    In addition to SR-55 mainline lane widening, additional improvements would include:

    • Standard shoulders for freeway and interchange ramps
    • Reconfiguration of various interchange ramps for increased ramp storage capacity
    • Additional through and turn lanes at ramp intersections
    • Improvements to nearby arterial street intersections affecting interchange operations
    • New and replaced structures including railroad overheads
    • Upgrades to existing flood channels and a storm drain bypass system

    The Costa Mesa Freeway, State Route 55 (SR-55), was constructed in 1962 as a four-lane highway. Within the next 10 years, another lane was added in each direction.

    In 1985, Orange County's first carpool lane was added to SR-55 between I-405 and SR-91 freeway. The freeway was also extended to 19th Street in Costa Mesa in the late 80s.

    With the help of Measure M, Orange County's half cent sales tax for transportation improvements, along with additional state and federal dollars, SR-55 continued to change.

    In late 1995, the freeway was widened between SR-22 and McFadden Avenue, and a direct carpool lane connector was added between I-5 and SR-55.

    From 1996 to 2002, Caltrans and OCTA completed the addition of one lane in each direction between I-5 and SR-91.

    Community Outreach

    The 55 Outreach Team is available to make a presentation to your neighborhood, organization or business. Feel free to contact us with your request, questions or comments by email or phone. You can also stay informed by visiting this page on a recurring basis or joining the project email list. We welcome your participation.

    The environmental phase will include a public review period. Additional information regarding a public hearing/meeting will be posted as soon as the date and location are available.

    Anticipated Schedule

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