Tram systems in San Diego
San Diego is a coastal city in southern California, close to the United States’ border with Mexico. Situated around San Diego Bay, it is an important naval, commercial and tourist centre, known for its beaches, Balboa Park and historic Old Town. Its urban area extends inland and southwards towards the border, where San Ysidro adjoins the Mexican city of Tijuana.
Public transport is centred on the San Diego Trolley light rail network and an extensive network of local and Rapid bus services, provided by the Metropolitan Transit System (MTS). The Trolley connects downtown with the Mexican border, the University of California San Diego, Mission Valley and communities in East County.
The San Diego Trolley comprises four regular light rail lines, identified by colour. The Blue Line links San Ysidro at the Mexican border with downtown and UTC via UC San Diego. The Orange Line connects downtown with El Cajon through the southeastern suburbs, while the Green Line reaches El Cajon via Old Town, Mission Valley and San Diego State University. The Copper Line provides a connecting service between El Cajon and Santee.
A fifth route, the Silver Line, provides a heritage service around a downtown loop on selected dates. It uses restored PCC streetcars and an original San Diego U2 light rail vehicle, offering a different experience from the regular network.
San Diego currently has 4 tram lines, details of which can be found on the Lines tab.
Metropolitan Transit System (MTS) is responsible for the Trolley network and much of the area’s bus transport. Trolley services are operated by its subsidiary, San Diego Trolley, Inc. The MTS website provides route maps, timetables, fare information and service updates.
Useful official links:
San Diego’s first streetcars began operating in 1886, using horse- and mule-drawn vehicles. An early electric service followed in 1887, initially linking downtown with Old Town, but the venture was short-lived. The city also briefly had a cable railway, which operated between 1890 and 1892 before its route was later converted to electric traction.
A more lasting electric network developed under John D. Spreckels, whose San Diego Electric Railway began operating in 1892. Its routes helped shape the city’s expansion, connecting downtown with developing neighbourhoods including Mission Hills, North Park and Kensington. Streetcars became an important part of everyday transport, supporting residential growth beyond the original city centre.
Competition from buses and private cars weakened the streetcar network during the 1930s. Modern PCC streetcars entered service in 1937, improving passenger comfort, but did not reverse the longer-term decline. Following the sale of the Spreckels transport business, the remaining streetcar services were replaced by buses in April 1949, bringing the original system to an end.
Planning for a new rail system gathered momentum during the 1970s. The Metropolitan Transit Development Board approved the feasibility of the Trolley project in 1978, and the acquisition of the San Diego & Arizona Eastern Railway in 1979 provided an existing railway corridor for much of the initial route. Reusing railway infrastructure helped make a comparatively economical return to electric passenger transport possible.
The modern San Diego Trolley opened on 26 July 1981, linking Santa Fe Depot in downtown San Diego with San Ysidro at the Mexican border. Known as the South Line, it used distinctive red light rail vehicles and established the foundation of today’s Blue Line. The project became an early example of the revival of modern light rail in the United States.
The network expanded eastwards to Euclid Avenue in 1986 and El Cajon in 1989. A downtown Bayside extension followed in 1990, serving the Convention Center area. Further extensions reached Santee in 1995, Old Town in 1996 and Mission Valley in 1997. The South and East lines adopted the Blue and Orange names in 1997.
The Mission Valley East extension opened in 2005, completing a route through Mission Valley to the eastern network and serving San Diego State University through an underground station. This enabled the introduction of the Green Line between Old Town and Santee. In 2012, Green Line services were extended through downtown along the Bayside route to 12th & Imperial.
The Silver Line began operating in 2011, returning restored PCC streetcars to downtown on a heritage loop. Separately, the Trolley Renewal programme modernised the older Blue and Orange line infrastructure, rebuilding stations and upgrading track, signalling and power equipment. Completed in 2015, the programme also enabled low-floor vehicles to operate throughout the regular network.
A major expansion opened on 21 November 2021, when the Mid-Coast extension carried the Blue Line northwards to UC San Diego and UTC. The project added approximately 11 miles (18 km) of railway and nine stations, providing a direct service between the international border and University City.
On 29 September 2024, the Copper Line was introduced between El Cajon and Santee, replacing the northern ends of the Green and Orange services. This reorganisation separated the outer East County service from the longer routes, helping prevent delays on that section from spreading across the wider network.
San Diego currently has 4 tram lines, which are listed below.
| Line | Description |
|---|---|
| Blue | The Blue line runs between San Ysidro Transit Center and UTC Transit Center via downtown San Diego, Old Town and UC San Diego. |
| Orange | The Orange line runs between Courthouse and El Cajon Transit Center via downtown San Diego, Encanto, Lemon Grove and La Mesa. |
| Green | The Green line runs between 12th & Imperial Transit Center and El Cajon Transit Center via the Convention Center, Old Town, Mission Valley and San Diego State University. |
| Copper | The Copper line runs between El Cajon Transit Center and Santee Town Center via Arnele Avenue and Gillespie Field. |
The San Diego Trolley uses standard-gauge track (1,435 mm) and overhead direct-current electrification. The network combines reserved railway corridors with street-level running through downtown, alongside elevated sections and a tunnel serving the underground station at San Diego State University.
Most routes are double-track, although the outer section between Gillespie Field and Santee includes single track. This operating constraint was an important reason for introducing the separate Copper Line service, reducing the spread of delays to the longer Green and Orange lines.
Parts of the network retain a connection with their origins as conventional railway corridors. Freight trains share certain tracks with the Trolley, operating outside passenger-service hours under arrangements managed by MTS.
Regular services use Siemens S70 and S700 articulated light rail vehicles, with low-floor entrances and raised seating areas over the outer bogies. The fleet includes the original, longer S70 vehicles and shorter versions developed to suit the network’s downtown street blocks. The shorter vehicles allow three-car trains to fit between intersections.
The newer S700 vehicles have a revised interior with a wider central aisle, improving circulation and providing more space for passengers travelling with bicycles or wheelchairs. The final high-floor SD100 vehicles were withdrawn from the active fleet during the financial year ending June 2025, completing their replacement in regular service.
Vehicles operate coupled together, with train length varying according to the service. The main routes commonly use three-car trains, while the Copper Line is operated with one or two cars.
The Silver Line has a separate heritage fleet comprising two restored PCC streetcars, numbered 529 and 530, and U2 car 1001, one of the original vehicles from the modern Trolley’s opening in 1981. These operate on selected dates around the downtown loop.
MTS is undertaking a major infrastructure renewal programme on the Orange Line between 32nd & Commercial and El Cajon Transit Center. Known as Rail Ready, the project includes replacement track, upgraded signalling and level-crossing equipment, and improvements to pedestrian crossings. The work is intended to reduce delays, improve reliability and strengthen safety along the existing route.
Construction began in June 2025 and is scheduled to continue until spring 2029. Work is being delivered in phases, with temporary weekend closures of individual sections and replacement bus services during these periods. The programme renews the existing railway without extending the line or adding stations.
An approved project at Rio Vista station on the Green Line will strengthen the retaining structures supporting the platforms and improve drainage and other station infrastructure. Construction is planned to begin in autumn 2026 and take approximately 30 weeks, with phased working intended to maintain Trolley service during the project.