State Route 78 (SR 78) serves as the primary east-west travel corridor between Escondido and Oceanside, traversing through the cities of Carlsbad, Vista, and San Marcos, as well as unincorporated areas of San Diego County. SR 78 serves as the primary route for local and regional travel in North County between these local jurisdictions and provides north-south connections to Interstates 5 and 15. SR 78 has experienced major congestion over the recent years as more and more commercial and residential growth has occurred. Back-ups are particularly frequent near the SR 78 and I-15 interchange. To address this increased congestion, a study to evaluate plans to improve SR 78 was completed in 2012 and construction improvements just west of the SR 78/I-15 interchange were implemented. For information on future improvements visit the I-5/SR 78 Interchange Project webpage.

SR 78 Corridor Study

In 2009, SANDAG was awarded a Caltrans Planning Partnership Grant to fund the examination of the feasibility of toll and other non-toll alternatives to address future regional and local travel demand within this regionally significant corridor, with the grant match provided by the City of San Marcos. The study examined two alternatives. Both alternatives included the addition of two new lanes on SR 78 (one eastbound, one westbound), auxiliary lane improvements, and transit and connector projects consistent with the 2050 Regional Transportation Plan. To learn more about the study, visit the SR 78 Corridor Study SANDAG project Web page.

SR 78 Construction Projects

Three improvement projects were constructed to reduce traffic congestion and improve traffic flow just west of the SR 78/I-15 interchange. These projects included the addition of east and westbound auxiliary lanes and ramp improvements, and rebuilding the Nordahl Road Bridge.

  • Westbound SR 78 Lanes: This project widened the connecting on-ramp from the I-15, adding a fifth westbound lane from the connector to Nordahl Road and adding a lane to the westbound Nordahl Road off-ramp. The project opened to traffic on January 19, 2012, and construction is now complete.

  • Eastbound SR 78 Lanes: This project added a lane between Woodland Parkway and Barham Drive on-ramps. Other improvements included adding two eastbound lanes between the Barham Drive on-ramp and the end of the off-ramp for Nordahl Road. Work began in January 2012 and the new lanes opened on May 1, 2013. 

  • Nordahl Road Bridge: This project replaced the original Nordahl Road Bridge. The new bridge has an additional two feet of clearance to allow taller trucks to pass under it. It is also one lane wider than the older bridge, which helps motorists make left hand turns from the bridge onto the highway. Also, the westbound and eastbound off-ramps to Nordahl Road were widened to include one additional turning lane to prevent vehicles from backing up onto the freeway. Work began in late February 2012 and the new bridge opened to traffic in November 2012.

What's New?

For questions, please call the I-15 Public Information Office at (619) 688-6670. To view the latest construction advisory or news release, click here.

SR 78 project video

SR 78 Project Map View

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