Blue Line (San Diego Trolley)

UC San Diego Blue Line

Company type	Light rail route
Industry	Public transportation
Founded	1981-07-26
Headquarters	San Diego , United States
Area served	San Diego metropolitan area
Owner	San Diego Metropolitan Transit System (MTS)
Parent	San Diego Trolley, Inc.
Website	www.sdmts.com

The Blue Line—officially known as the UC San Diego Blue Line due to sponsorship—is a light rail route within the San Diego Trolley network, managed by San Diego Trolley, Inc., a branch of the San Diego Metropolitan Transit System (MTS). Covering an entire journey in approximately 83 minutes, it connects the UTC Transit Center with the San Ysidro Transit Center, located near the San Ysidro Port of Entry at the Mexico–United States border, facilitating international transit. This line serves prominent areas such as La Jolla, downtown San Diego, National City, Chula Vista, and San Ysidro, making it the longest route within the system.

Among the five lines—Blue, Orange, Green, Copper, and the weekend-only Silver—the Blue Line records the highest ridership, with 24,389,986 passengers annually (roughly 75,160 daily) during fiscal year 2024. Its current name reflects a $30 million naming rights agreement with UC San Diego Health. A major extension to the University of California, San Diego campus, adding nine new stations, commenced operations on November 21, 2021, significantly improving access to this key academic and research institution.

History

The Blue Line of the San Diego Trolley began operations on July 26, 1981, originally running from Centre City San Diego to San Ysidro at a total expense of $86 million. This route utilized pre-existing tracks from the San Diego and Arizona Eastern Railway, which had been acquired from Southern Pacific in 1979 for $18.1 million.

In 1986, to differentiate it from the newly introduced East Line (later renamed the Orange Line), this line was rebranded as the South Line. On July 2, 1992, its northern reach was extended to County Center/Little Italy station. With the addition of the Old Town extension in 1996, it adopted the name North-South Line before being designated as the Blue Line in 1997, coinciding with an expansion toward Mission San Diego.

Following the launch of the Green Line in 2005, Blue Line service was reduced to terminate at Old Town Transit Center. During peak hours, trains continued to Qualcomm Stadium and San Ysidro until September 3, 2006; these runs were discontinued due to duplication with Green Line service. Subsequently, all Blue Line trains ended their routes at Old Town.

Several station modifications occurred over time: in 1986, San Diego Square station was closed due to low usage and its proximity to Fifth Avenue station. That same year saw E Street station open in Chula Vista and Centre City station renamed Fifth Avenue. Fenton Parkway station was introduced in 2000 as an infill station but currently serves only the Green Line along with other stations on the Mission San Diego corridor.

2012 realignment

On September 2, 2012, Blue Line service between America Plaza and Old Town was ceased, establishing America Plaza as its northern endpoint. Trains ran between America Plaza and San Ysidro every 15 minutes, with frequencies increasing to every 7½ minutes during weekday peak periods. Service to Old Town resumed following completion of the Mid-Coast trolley extension reaching UC San Diego. In 2015, UC San Diego Health contributed $30 million for naming rights, resulting in the route being titled the UC San Diego Blue Line.

Trolley Renewal Project

To accommodate the introduction of new Siemens S70 vehicles on the Blue Line, extensive station upgrades were required and carried out over a five-year span to limit service interruptions. The Trolley Renewal Project began in autumn 2010, focusing on enhancements to tracks and stations along both the Blue and Orange Lines. Following their initial deployment on the Green Line in 2011 and the Orange Line in 2013, low-floor Siemens S70 light rail vehicles started service on the Blue Line as of January 27, 2015. The project wrapped up with the completion of track and station improvements by late 2015.

Mid-Coast extension

The Mid-Coast Corridor Transit Project expanded the Blue Line by extending it from Old Town Transit Center to La Jolla Village, University of California San Diego (UCSD), and University City. Forecasts estimate ridership will reach 34,700 daily trips by 2030. This extension primarily follows the Coaster rail corridor and Interstate 5, incorporating an elevated segment near UCSD. Construction expenditures were projected at $2.1 billion. The expansion aims to alleviate parking demand on the UCSD campus while offering direct trolley access to Westfield UTC, a prominent shopping destination. The SuperLoop BRT Shuttle continues to link the UTC vicinity with adjacent trolley stations. Testing operations commenced in June 2021, with revenue service beginning November 21, 2021; however, some late-night Blue Line trips still conclude at America Plaza.

This initiative was coordinated alongside the North Coast Corridor project, which involves upgrades to the LOSSAN Rail Corridor further north. Both projects utilize the historic Surf Line right-of-way originally established in the 1880s to connect Los Angeles and San Diego.

Overnight Express bus

On January 26, 2025, MTS introduced bus route 910, branded as an Overnight Express service operating along the southern Blue Line corridor between midnight and 5 A.M., covering hours when Blue Line trolleys are not running. Route 910 links and San Ysidro Transit Center, stopping at key transit hubs such as , , , , and .

Stations

Station	Location	Connections
	University City, San Diego	Template:Bus icon MTS: Template:SDMTS route, Template:SDMTS route, Template:SDMTS route, Template:SDMTS route, Template:SDMTS route, Template:SDMTS route, Template:SDMTS route, Template:SDMTS route, Template:SDMTS route Template:Bus icon NCTD: Template:NCTD route Template:Parking symbol Park and ride: 333 spaces, paid
		Template:Bus icon MTS: Template:SDMTS route, Template:SDMTS route, Template:SDMTS route, Template:SDMTS route
		Template:Bus icon UC San Diego Triton Transit: Health Campus Connector, Regents Express Template:Rint FlixBus UC San Diego – La Jolla
	La Jolla, San Diego	Template:Bus icon MTS: Template:SDMTS route Template:Bus icon UC San Diego Triton Transit: Inside Loop, Outside Loop, Regents Express
		Template:Bus icon MTS: Template:SDMTS route, Template:SDMTS route, Template:SDMTS route Template:Bus icon NCTD: Template:NCTD route Template:Parking symbol Park and ride: 289 spaces
	Bay Park, San Diego	Template:Bus icon MTS: Template:SDMTS route, Template:SDMTS route, Template:SDMTS route Template:Parking symbol Park and ride: 227 spaces
		Template:Bus icon MTS: Template:SDMTS route
	Morena, San Diego	Template:Parking symbol Park and ride: 279 spaces	-

Station	Location	Connections

Station	Location	Connections

Station	Location	Connections

Station	Location	Connections

Station	Location	Connections

Station	Location	Connections

Station	Location	Connections

Station	Location	Connections

Station	Location	Connections

}

Proposed Cross-Border Trolley

Currently, the Blue Line ends at the San Ysidro Transit Center, located just north of the Mexico–United States border. However, there are plans awaiting approval to extend the line further into Tijuana. This extension would involve constructing roughly of elevated track leading to a new station in Tijuana. Supported by SANDAG and officials from Baja California, the "Cross-Border Trolley" initiative seeks to improve transit connections across the border and is expected to require up to eight years for completion.