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. To learn more about the completed SR 78 Corridor study, visit the SR 78 Corridor Study project webpage.

SANDAG and Caltrans have proposed additional improvements for the SR 78 corridor, including the I-5/SR 78 Interchange, I-15/SR 78 Express Lanes connectors, SR 78 HOV/Express Lanes, Woodland/Barham Interchange, and additional operational improvements along SR 78. Other projects include future double tracking and express services for the SPRINTER and the construction of additional segments of the Inland Rail Trail Bike Path.


Upcoming Projects

SR 78 Corridor MapI-15/SR 78 Interchange Project  

Environmental studies are currently underway for constructing a direct connector between I-15 and SR 78 Express Lanes. The project would connect the existing I-15 Express Lanes with the proposed future managed lanes on SR 78 from the Twin Oaks Valley Road overcrossing to the I-15 junction. By providing the proposed managed lanes and connector,  Express Lanes traffic could avoid the weaving and queuing that occurs as vehicles enter and exit the facility at the existing interchanges.  

The proposed connector is listed as the top priority among direct connector projects in the SANDAG 2050 Regional Transportation Plan. The project has an estimated cost of $350 million and is currently scheduled for construction in 2025.

Woodland/Barham Interchange

The City of San Marcos and Caltrans are working together to redesign the existing East Barham Drive/Woodland Parkway interchange located in the City of San Marcos.  The project will reduce traffic congestion, increase roadway capacity, and improve safety.  The project’s primary objective is to improve access to and from the freeway as well as to improve access for local vehicle, bicyclists, and pedestrians across the freeway.

This project includes interchange improvements that will widen or replace the East Barham Drive/Woodland Parkway undercrossing, widen and realign local streets in the immediate interchange area, widen and realign the westbound on- and off-ramps and eastbound off-ramp, relocate the eastbound on-ramp adjacent to the eastbound off-ramp, and signal upgrade the Rancheros Drive/westbound ramps, Woodland Parkway/eastbound ramps, Woodland Parkway/East Barham Drive, and the Woodland Parkway/Rancheros Drive intersections. Construction is anticipated to begin by 2025.

SR 78 Asset Management

Improvements have been planned and are anticipated to be implemented in the near future along eastbound and westbound SR 78. Activities include pavement resurfacing, bridge rails, ADA ramps, culvert restoration, and a new westbound auxiliary lane between Nordahl and Twin Oaks Valley roads in San Marcos. Intelligent Transportation System technology improvements will help prepare for an automated future, improve traveler information, and reduce congestion and emissions.

In addition, Caltrans completed construction on eastbound and westbound auxiliary lanes between Twin Oaks Valley Road and East Barham Drove in 2018.