I-5/SR-78 Interchange Improvements Project: PA&ED Phase

In preparation for the environmental document, Caltrans invites the public to provide initial comments on the proposed project and potential environmental impacts to study.

Participate

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 today’s traffic demand. Heavy westbound SR-78 traffic trying to access southbound I-5 often exceeds the intersection capacity, causing backups that extend onto SR-78. This congestion also leads some drivers to divert onto local streets, increasing traffic in nearby communities. Additionally, the short distance between this freeway-to-freeway interchange leads drivers to complete quick lane changes, creating weaving that slows traffic and reduces safety on both I-5 and SR-78.

The project objectives are:

  • Safety and Traffic Operations: Reduce or eliminate conflicts at the I-5/SR-78 interchange to enhance safety and operations. Improvements will reduce conflicting movements and provide direct connectors for general-purpose lanes or managed lanes, as deemed necessary and feasible.
  • Improve Traffic Flow Between Closely Spaced Interchanges: Minimize conflict points caused by the proximity of interchanges. This will help reduce weaving, support smoother merging and diverging movements, and may include access modifications, advanced signage, and auxiliary lanes.
  • Design standards: Improve interchange design to current Caltrans standards.  
  • Encourage Sustainable Transportation: Incorporate features that promote carpooling, vanpooling, transit, pedestrian, and bicyclist, contributing to reduced congestion and environmental benefits, specifically contributing to lower emissions.
  • Natural Resources and Community Livability: Strive to demonstrate a balanced approach that considers responsible stewardship of natural resources in relation to the project scope, while supporting community livability within the project area.

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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Plan

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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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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Preliminary Project Scoping

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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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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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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Construction

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