I-5/SR-78 Interchange Improvements Project: Project Approval and Environmental Document Phase

In preparation for the environmental document, Caltrans is conducting technical and environmental studies and seeking public input on the proposed project and potential environmental impacts to be studied.

Comment

Project Description: 

The purpose of the Interstate 5/State Route 78 (I-5/SR-78) Interchange Improvements Project is to improve safety and traffic flow at the interchange.

The I-5/SR-78 interchange is currently controlled by traffic signals and no longer handles current traffic volumes. Heavy westbound SR-78 traffic heading to southbound I-5 often exceeds the intersection’s capacity, causing backups that can extend onto SR-78. This congestion can also cause drivers to use local streets, increasing traffic in nearby neighborhoods. In addition, the short distance between nearby ramps and connections requires drivers to make quick lane changes, creating weaving movements that slow traffic and reduce safety on both I-5 and SR-78.

The project objectives are:

  • Improve Safety and Traffic Operations: Reduce or eliminate conflict points at the interchange to improve safety and traffic flow. This may include new direct connectors for general-purpose or managed lanes, if feasible.
  • Improve Traffic Flow Between Nearby Interchanges: Reduce weaving and merging conflicts caused by the close spacing of ramps and interchanges. Improvements may include access changes, better signage, and auxiliary lanes.
  • Meet Current Design Standards: Update the interchange to current Caltrans design standards.
  • Support Sustainable Transportation: Include features that encourage carpooling, vanpooling, transit, walking, and biking. These improvements can help reduce congestion and lower emissions.
  • Protect Natural Resources and Community Quality of Life: Balance transportation improvements with responsible environmental stewardship and support for nearby communities.

Project Schedule: 

  • Preliminary Planning: 2012-2021
  • Environmental: 2024-2029
  • Public review that will inform the Environmental Impact Report/Environmental Assessment (EIR/EA) scheduled for spring of 2025.
  • Environmental Impact Report/Environmental Assessment (EIR/EA) expected to be complete by 2029.
  • Design 2029-2034
  • Construction 2034-2038 (pending funding)

Map: Map of the project area

Funding and Cost: 

The proposed I-5/SR-78 Interchange Project is federally funded for the initial planning and environmental efforts.

$8 million is available for Preliminary Design and Environmental Studies for 2024-2029, and $50 million for Design in 2029-2034.

Over the next few years as project alternatives are refined, additional funding will need to be identified for Design and Construction. 

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complete

Project Initiation

Beginning in 2014, Caltrans met with jurisdictions located within or adjacent to the project's proposed work limits (Oceanside, Carlsbad, and Vista) to discuss the project's proposed scope, and to present and obtain feedback on the initial alternatives developed by the Caltrans Project Team.

The Project Study Report, completed in Fall 2021, updated the proposed alternatives in the Preliminary Engineering Studies (PES) to six Build alternatives and one No Build based on certain criteria for improving travel time and enhancing communities in the area. In 2020, Caltrans added operational improvements as an additional project solution. 

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Notice of Preparation (NOP)

As required by the California Environmental Quality Act (CEQA), the project Notice of Preparation (NOP) will be filed on Wednesday April 29th, 2026. The NOP advises the public that the environmental review process has begun and invites the public to provide initial comments on the proposed project and potential environmental impacts that will be studied. The 30-day public scoping period runs from April 29 to May 29th, 2026, and an in-person public scoping meeting will be held on Wednesday May 13, 2026.

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Alternatives Analysis

As part of preliminary project scoping, Caltrans continues to hold meetings with local cities and partners to develop and review schematic concept alternatives. Also, during the Project Approval and Environmental Document (PA&ED) phase, additional opportunities will be available for public involvement and feedback.

These engagement activities are designed to foster collaboration, transparency, and meaningful input from community members, businesses, and city representatives. Regular updates will be shared to ensure that residents, businesses, and city stakeholders remain aware of important developments and next steps.

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planned

Project Approval and Environmental Document

The project team anticipates releasing the Draft EIR/EA in January 2029, at which point a public hearing and additional public comment period will be held to gather specific input on the Draft Environmental Document. The Final EIR/ EA is anticipated for publication in October 2029.

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planned

Final Project Design

As part of the final project design, Caltrans will continue to engage local cities and communities as it relates to the preferred Alternative. Final design is anticipated to conclude in 2034.

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planned

Construction

As part of the Project construction, Caltrans will continue to provide Public Affairs Liaison updates.