Commuters in North County know full well the traffic headache caused by the Interstate 15 and state Route 78 interchange.
Caltrans plans to build a connector express lane from I-15 to SR-78 through San Marcos, and a draft environmental impact report (EIR) was recently completed.
“This project will reduce congestion and travel times in the area, as well as encourage the usage of carpool,” Caltrans North County Corridor Director Victor Mercado said.
Right now, to get onto SR-78 from the express lanes on I-15, drivers have to cross over five lanes of traffic and, at the same time, dodge incoming traffic from West Valley Parkway.
That’s why Caltrans, the San Diego Association of Governments (SANDAG) and the city of San Marcos want to build a connector ramp between the existing express lanes and three miles of newly proposed express lanes on SR-78.
“By providing these direct connectors between the I-15 express lanes and future express lanes on state Route 78, it'll reduce or eliminate that that movement of traffic,” Mercado said.
That interchange produces most of the traffic congestion for westbound SR-78 and more than half of the traffic exits within the first three offramps.
Mercado said it was a balancing act determining how much of the newly proposed express lanes on SR-78 to build.
“How much is it going to cost, and then the impacts to the congestion in the area?" he said. "So, building three miles was considered and determined that was enough to provide traffic relief in that section of the highway.”
This project has been in the works for a while. The environmental impact study began in 2019. Now that the draft is out, Caltrans is asking for feedback from the public.
“It's there to make it better for drivers, but more importantly, to provide transportation options and alternatives to the community, not just for the people who are driving, but people that use public transportation as well as active transportation modes like pedestrians and bicyclists,” Mercado said.
In addition to the express lanes, the project will include reconstructing the Barham Drive and Woodland Parkway interchange to accommodate the new lanes, as well as a fully separated pathway for bicyclists and pedestrians.
The project is expected to cost $490 million and could be completed by 2030. But right now, Caltrans has enough funding through the design phase and the rest of the funding is pending.
For now, residents can click here to view the draft EIR. The deadline to submit comments is July 7, 2025.
