I-5/SR 78 Interchange Project

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Concepts to improve the Interstate 5 (I-5)/State Route 78 (SR 78) interchange in the cities of Oceanside and Carlsbad in San Diego County are currently being evaluated by Caltrans. Currently, motorists experience traffic delays at the interchange where there is a lack of direct freeway-to-freeway connections. These connections are currently made via a traffic signal at the I-5 southbound ramps/Vista Way intersection.

Project Objectives:

  • Reducing travel times and congestion through the interchange for local and regional commuters;
  • Enhancing multi-occupant vehicle connectivity between I-5 and SR 78; and
  • Protecting and/or enhancing the human and natural environment in the project vicinity where feasible.

Potential interchange improvements being studied include:

  • Adding direct freeway-to-freeway connectors from southbound I-5 to westbound SR 78 and westbound SR 78 to southbound I-5;
  • Building direct access ramps that connect to future carpool and transit vehicle lanes on I-5 and SR 78; and
  • Reconfiguration of the existing interchange to accommodate the new connections outlined above.

Environmental Review Process

Caltrans is studying various options to improve the interchange. More than 20 options were analyzed as part of the preliminary feasibility study. Caltrans hosted a public workshop on January 29, 2015, at the Carlsbad Senior Center, to gain initial feedback from members of the public about the project.


Caltrans plans to hold a public scoping meeting to formally kickoff the project’s environmental review process in early 2016. At that meeting, the public will be available to view project alternatives that could be studied as part of the environmental review process. The public scoping meeting initiates a 30-day public review and comment period. Caltrans anticipates the release of the Draft Environmental Impact Report/Environmental Impact Studies (EIR/EIS) in 2018-2019. 

Key Documents


sr 78 fact sheet    I-5/SR-78 Interchange FAQ    Jan. 29 Public Workshop Displays
public workshop displays
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