Since opening in 2021, the extension has provided nearly 24 million passenger trips, expanded transit access, and advanced the region's climate goals
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San Diego – November marks the fifth anniversary of the Mid-Coast Trolley Extension, and the San Diego Metropolitan Transit System (MTS) and San Diego Associations of Government (SANDAG) are commemorating a project that has transformed mobility across the San Diego region by connecting communities, educational institutions, employment centers and major destinations through high-quality transit service.
Officially opening on Nov. 21, 2021, the Mid-Coast Trolley Extension added 11 miles of new Trolley service and nine stations to the UC San Diego Blue Line, creating a one-seat ride between the U.S.-Mexico border and University City. Since opening, the extension has provided more than 23.9 million passenger trips, helping residents, students, workers and visitors travel throughout the region while reducing greenhouse gas emissions and roadway congestion.
"The Mid-Coast Trolley Extension has delivered exactly what riders and regional leaders envisioned: a fast, reliable and sustainable transportation option connecting people to jobs, schools, healthcare and recreation," said Stephen Whitburn, Chair of the MTS Board of Directors and San Diego City Councilmember. "Five years later, millions of riders have embraced the service, demonstrating the value of investing in transportation infrastructure that improves quality of life and strengthens our communities."
Today, the extension serves approximately 500,000 riders each month and generates an estimated 5.4 million annual passenger trips. Trains operate every 15 minutes throughout the day, providing a convenient transit connection between San Ysidro, the South Bay, Downtown San Diego, UC San Diego, University City and surrounding communities. Riders can reach UC San Diego Central Campus from San Ysidro in about 77 minutes and the UTC Transit Center in about 83 minutes, all on a single ride.
The extension has become an important mobility resource, carrying approximately 21% of all UC San Diego Blue Line ridership. Since opening, MTS has operated more than 61.7 million revenue miles and provided approximately 1.2 million train service hours along the corridor. The extension has also helped MTS move up in national transit ridership rankings from 21st in 2019 to 13th in 2026.
"The Mid-Coast Trolley Extension of the UC San Diego Blue Line is one of the most significant transportation investments in our region's history," said SANDAG Chair and Solana Beach Mayor Lesa Heebner. "Today, thousands depend on it as part of their daily routines, a testament to how seamlessly it has become integrated into the way people move throughout our region. Its success demonstrates what can be achieved through long-term vision, thoughtful planning, and strong partnerships, and sets a new standard for what our region can accomplish through collaboration and a shared vision for the future."
Beyond improving mobility, the Mid-Coast Trolley Extension has helped advance regional sustainability goals. The project is estimated to have helped the region avoid approximately 70,000 metric tons of carbon dioxide emissions since opening and continues to reduce greenhouse gas emissions by roughly 16,000 metric tons annually by providing a cleaner alternative to driving.
The $2.17 billion Mid-Coast Trolley Extension, delivered by SANDAG, was one of the largest transportation infrastructure projects in San Diego County history. At the time, the project employed more than 5,200 onsite workers. The project was funded through a combination of federal, state and local sources, including approximately $1.04 billion from the Federal Transit Administration's New Starts program, state transportation funds and TransNet, the region's voter-approved half-cent sales tax administered by SANDAG for transportation improvements.
To commemorate the milestone, regional leaders, community members and project partners gathered Nov. 7 at UC San Diego to celebrate five years of service and recognize the lasting impact the extension has had on mobility, sustainability and economic opportunity throughout the San Diego region.
About MTS
The Metropolitan Transit System (MTS) operates 93 bus routes and four Trolley lines in 10 cities and unincorporated areas of San Diego. MTS is a leader in advancing initiatives to create a greener, cleaner and better-connected transit system in San Diego. Each weekday, more than 250,000 passenger trips are taken throughout the MTS system, taking people to work, school, health appointments and other essential trips. In FY 2026, MTS served more than 81 million riders. In 2026, MTS was recognized by the American Public Transportation Association (APTA) as the Outstanding Public Transportation System in North America among agencies providing 50 million or more annual passenger trips. For service schedule updates, news, alerts and more information on how you can use public transportation, go to www.sdmts.com.
About SANDAG
SANDAG is the regional agency that connects people, places, and innovative ideas by implementing solutions with our unique and diverse communities. We are committed to creating a San Diego region where every person who visits, works, and lives can thrive. SANDAG.org
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