The original concept of the SLRV came to fruition in the late 1960s as the limited number of cities with PCCs in North America were looking for modern replacements for their aging rolling stock; the last PCC had been manufactured in 1952.

[4] Meanwhile, Muni in San Francisco, released a request for proposals in 1971 to purchase 78 new cars, designed by the rail transit engineering firm Louis T. Klauder and Associates (LTK), to replace their aging PCC fleet.

[5] The new cars, which Muni called subway-streetcars, were touted as "specially designed for San Francisco, adaptable to both subway and surface conditions and seating more passengers than the present [PCC] streetcars.

[10] Instead, Boston (MBTA) was directed to join with San Francisco (Muni) and Philadelphia (SEPTA) to design a new streetcar that could meet the needs of all three cities.

[5] The Standard Light Rail Vehicle (SLRV) specification was developed by UMTA based on the 1971 LTK design for Muni in conjunction with potential operators (who were all currently operating PCCs) in Boston, San Francisco, Philadelphia (SEPTA), Cleveland (Shaker Heights), Pittsburgh (Port Authority), New Jersey, El Paso (City Lines), and Toronto (TTC) as well as industry consultants at Parsons Brinckerhoff and Louis T. Klauder and Associates.

[25] The Greater Cleveland Regional Transit Authority tested MBTA car #3401 on former interurban lines in mid-1976, but ultimately declined to purchase the US SLRV, instead buying custom LRVs of a different design from Breda Costruzioni Ferroviarie.

[28] While Pittsburgh, New Orleans, and Newark collaborated with UMTA in designing the SLRV[citation needed], and already had traditional streetcars, they ultimately did not buy the cars, nor would any newly built light rail systems such as San Diego.

[29] New Orleans, which had never adopted the PCC design, continues to operate its 1920's vintage Perley Thomas-built streetcars, supplemented by modernized custom-built replicas of the cars.

A major newspaper story emerged when a reporter and a photographer managed to get into a section of the Green Line's subway which was not in use at the time and found it was full of cannibalized cars which had been abandoned in the tunnel.

After the story broke, out-of-service SLRVs began to appear in several storage yards which were easily viewed by the public, though this may have simply been due to the ever-increasing number of disabled cars.

[33] On October 9, 1978, MBTA rejected the final 40 SLRVs and directed Boeing-Vertol to retrieve the 35 cannibalized cars, concluding that poor fleet reliability meant that Boeing was in breach of warranty.

[33] On December 15, 1978, MBTA and Boeing signed an agreement that revised specifications to enable the full delivery of 175 SLRVs,[9]: 20  but reliability issues continued through 1979.

[13] Boeing made an offer in September 1979 which identified specific design issues that would be corrected at its expense, including leaking gearboxes, air conditioning compressor issues, and traction motor failures, but MBTA rejected the offer; around this time, MBTA hired product liability attorney and law professor William Schwartz to negotiate on its behalf[13][35] in August 1979.

[13][14] At the time of the settlement, 41 of MBTA's 135 SLRVs were inoperable due to design issues, accidents, and/or cannibalization for parts, which would require an estimated US$15,600,000 (equivalent to $65,490,000 in 2023) to restore to operating condition.

[1] The dimensions of the SLRV were determined by the existing track constraints of three proposed operators: MBTA (Boston), Muni (San Francisco), and SEPTA (Philadelphia).

[1][41] The cushion is 3⁄16 in (4.8 mm) thick and is injected in the threaded space between the rim and hub; the design was developed by Standard Steel and BART in the 1960s.

[18] The trucks are equipped with rubber chevron springs and pneumatic suspension, which automatically adjusts to maintain floor height with varying loads.

After production was ended by Boeing, Tokyu Car Corporation built light rail cars for Buffalo Metro Rail which externally resemble the SLRV, but many differences, most noticeably the lack of articulation, use of external steps for low-platform boarding instead of internal steps, and the use of single-leaf pocket doors similar to the London Underground D Stock.

Boeing Vertol's customary client (US Department of Defense) was relatively budget insensitive, more tolerant of cost overruns, and had sufficient funding and workforce to conduct complex maintenance, all contrary to the needs and abilities of a municipal transit agency.

[45] Boeing marketed the SLRV as a system and took the role of an integrator, subcontracting the design and fabrication of major components to external suppliers from places as far as Germany, Japan, and the United Kingdom.

This approach created uncertainty in component delivery dates and essentially precluded prototype testing in favor of meeting contracted schedule milestones, turning MBTA and Muni into, effectively, beta testers for the SLRV.

[51] The successor vehicles in Boston (Kinki Sharyo Type 7) and San Francisco (Breda LRV2/3) closely follow the specifications and performance of the SLRV.

With the introduction of Type 7s, the MBTA was finally able to retire most of its aging PCC cars, which had to remain in service much longer than originally planned due to the unreliability of the Boeings.

In order to make room for the new Kinki Sharyo Type 7 cars, Boston's MBTA instituted its first SLRV scrapping program beginning in 1987.

By the end of 1988, nineteen cars had been removed from the property, most of which had been in dead storage since the late 1970s and the remainder were victims of major collisions or derailment damage.

[citation needed] Kinki Sharyo would subsequently go on to produce LRVs for Dallas, San Jose, Phoenix, Seattle, and Los Angeles.

While both the Boeings and Type 7 Kinki Sharyo cars have wide door openings and reserved wheelchair spaces that make them compliant with the Americans with Disabilities Act, Boston's proposed Type 8 car would have a portion of its floor lower to the ground, allowing riders using wheelchairs to board without the need for a lift or mini-high platform.

However, the new Type 8s had been prone to derailing and other technical defects, which had significantly delayed their entry into service, and the MBTA nearly suspended the contract; at that point, the 55 rehabilitated SLRVs were still on the active roster, nearly a third of all Green Line rolling stock.

With capacity problems foreseen and thus requiring a short term solution, the Greater Manchester Passenger Transport Executive approached Muni about the possibility of buying redundant Boeing SLRVs.

[65][66][67] Upon arrival in England in January 2002, 1226 was sent to Derby Litchurch Lane Works for assessment by Her Majesty's Railway Inspectorate to ensure it met UK safety standards, while 1326 was delivered directly to Metrolink's Queens Road Depot.