Westbound SR-78 Will Fully Close Overnight in San Marcos Oct. 12–15

All westbound State Route 78 lanes at South Rancho Santa Fe Road in San Marcos will close overnight from Monday, Oct. 12, through Thursday, Oct. 15, 2026. Caltrans schedules each closure from 10 p.m. to 5 a.m. while crews replace weigh-in-motion concrete slabs.

The work affects westbound traffic traveling through the North County corridor between Escondido, San Marcos and Oceanside. The schedule may change because of weather, traffic incidents or other construction conditions.

The official detour

Westbound drivers will exit SR-78 at South Rancho Santa Fe Road and may re-enter the freeway from the westbound on-ramp at the same interchange. Portable message signs will direct traffic.

Location: westbound SR-78 at South Rancho Santa Fe Road, San Marcos.
Dates: Monday through Thursday nights, Oct. 12–15.
Hours: 10 p.m. to 5 a.m.
Detour: use the South Rancho Santa Fe Road off-ramp and return via the westbound on-ramp.

What nearby residents and businesses should expect

Caltrans says neighborhoods and businesses near the interchange may experience additional detour traffic, construction lighting and overnight noise. Required backup alarms will also be audible while construction vehicles operate. Crews will work to reduce impacts where possible.

Drivers should slow down, follow temporary signs and avoid distractions around the work zone. Check Caltrans QuickMap before departure for current closure and traffic information.

Part of a 17.7-mile SR-78 project

The closure is part of the SR-78 Asset Management Project covering 17.7 miles from Interstate 5 in Oceanside to Broadway and Lincoln Parkway in Escondido. Caltrans says the project is intended to preserve existing pavement and infrastructure, improve safety and modernize the corridor.

The estimated $126 million project includes $111.5 million in federal funding—$9.2 million of it from the Infrastructure Investment and Jobs Act—and $14.5 million in state funds.

California58 readers can also review the statewide work-zone safety guidance issued by Caltrans and explore more destinations in the San Diego County travel guide.