Plans to extend the line north to Pasadena in the San Gabriel Valley surfaced in the 1980s but were postponed due to funding constraints.

Planning for the northern extension resumed in the early 2000s as part of the Regional Connector Transit Project, with construction starting in 2014.

Subsequently, the L Line ceased service, and as part of the project, three additional downtown stations opened in the constructed tunnel alignment.

After this station, the line continues west, crossing over the San Gabriel River and underneath the I-605 freeway, diverging from I-210 and entering Duarte, before stopping at Duarte/City of Hope station located on the north side of Duarte Road, across from the City of Hope National Medical Center.

From here, the line continues, with a handful of stations serving the hillside areas north of downtown, including Lincoln Heights, Mount Washington, and the Southwest Museum of the American Indian.

At Union Station, passengers can transfer to the B and D rapid transit lines, Metrolink commuter rail, Amtrak, and buses.

The Regional Connector tunnel connects to the north end of 7th Street/Metro Center station, the former northern terminal of the A Line.

Along the corridor, there are some flyovers to either eliminate grade crossings in more densely populated areas or pass over diverging freight tracks.

[7] The full travel time of the 48.5-mile (78.1 km)[2] line is approximately two hours, including a brief layover at Union Station to change train crews.

The old route gave the new light rail trains a private right of way between Washington and Willow Street stations allowing them to reach higher speeds between stops.

[17] The route reached full capacity after one decade of service, and from 1999 to 2001, the Blue Line underwent a US$11 million project to lengthen 19 of its platforms to accommodate three-car trains.

[18] There were also plans since the 1980s to extend the Blue Line north to Pasadena but the connection through downtown was postponed due to funding constraints from the voter-approved 1998 Proposition A.

The proposition restricted local county subway funding, halting the process of the Blue Line extension and other rail transit projects from advancing.

[3][4][20] The renovation helped improve the line's speed and reliability by replacing and modernizing old tracks, signals, train control systems, and bridges.

It was eventually taken over by the Atchison, Topeka and Santa Fe Railway, as part of the Pasadena Subdivision, which saw Amtrak service until 1994, when construction began on the conversion to light rail.

However, the mostly above-ground segment of the extension from Union Station to Pasadena advanced and began construction in 1994 as a separate line but was suspended again by 1998 due to the Proposition A ban.

A groundbreaking ceremony for Phase 2A was held on June 26, 2010; construction began the following summer and was completed in September 2015, with the extension entering service on March 5, 2016.

The southern (Pico/Aliso–East LA) segment was combined with the existing E Line between Downtown Los Angeles and Santa Monica.

[38][39][40] The Southeast Gateway Line is a planned light rail line, mostly following the Pacific Electric's historic West Santa Ana Branch, connecting Downtown Los Angeles to the city of Artesia, along with other cities in southeastern Los Angeles County.

Both have problems: it would be difficult or impossible to lengthen some of the station platforms, and the number of trains already causes delays for other vehicles at level crossings.

Since the opening of the Regional Connector, ridership on the A Line continues to increase, potentially resulting in even more capacity problems.

The wye junction at Flower and Washington is a similar bottleneck, as trains on both lines must cross a busy intersection and freeway onramp at-grade.

[46] In 1998, the MTA commissioned Booz Allen Hamilton, Inc. to evaluate the cause of Blue Line collisions and recommend affordable solutions.

The high ridership results in increased pedestrian traffic near stations compared to other light rail systems.

In addition, although MTA Operations does not allow high passenger loads to dictate safe operations, there is pressure to maintain travel times and headway schedule requirements (e.g., a passenger trip from Los Angeles to Long Beach in less than one hour).Other contributing factors identified were the high population density leading to more pedestrian and vehicular traffic around the tracks, the diverse, varied socio-economic community around the line that creates literacy and language difficulties for public education campaigns, driver frustration due to the slow traffic speeds around the line that leads to more risk-taking behavior, and the shared right of way with freight traffic in the fastest running section from Washington station to Willow station, where trains operate at a maximum of 55 mph (89 km/h) between stations.

[50] Division 11 is located at 4350 East 208th Street in Cota, North Long Beach between Del Amo and Wardlow stations.

The facility can house and maintain 86 light rail vehicles and can perform heavy maintenance including repainting.

Northbound trains can enter and exit the yard via the cross tracks on the north and south sides of the junction.

These light rail vehicles were nearly identical to the older P865 model but were about five years newer and originally had equipment for automatic train operation.