The rolling stock of the Bay Area Rapid Transit (BART) system consists of 782 self-propelled electric multiple units, built in four separate orders.

With the withdrawal and retirement of the older fleet, there will be 775 vehicles in total, with long-term goals of eventually increasing this to 1,200 cars.

The eBART extension was constructed to more traditional specifications and uses Stadler GTW articulated diesel multiple units previously utilized in other systems.

To be able to maintain the vehicles until they are taken out of service, the workshop regularly procures computers on the second-hand market that can still address the old systems.

[9][10][11] Just as BART had realized in the mid-1970s that it had ordered too many A cars, it also learned that it took more time than desired to change the length of a train.

Among the changes were a conversion from DC to AC propulsion (detailed below), rebuilt trucks and suspension, and a complete cleaning and repair to the exterior and interior of the cars.

Because one of the original design goals was for all BART riders to be seated, the older cars had fewer provisions such as grab bars for standing passengers.

In the late 2000s BART began modifying some of the C2 cars to test features such as hand-straps and additional areas for luggage, wheelchairs and bicycles.

It was reported in 2011 that several strains of molds and bacteria were found on fabric seats on BART trains, even after wiping with antiseptic.

The Rohr cars were rebuilt with ADtranz model 1507C 3-phase alternating current (AC) traction motors with insulated-gate bipolar transistor (IGBT) inverters.

[25] The HVAC systems on the Rohr BART cars before rehabilitation were built by Thermo King, when it was a subsidiary of Westinghouse.

[27] According to BART, the noise in the tunnel used to be "compared to banshees, screech owls, or Doctor Who's TARDIS run amok".

[29][30] Critics have countered that this study analyzed straight, above-ground portions of different systems throughout the country at 30 mph (48 km/h), which is not representative of actual operating conditions.

Much of BART is under ground and curvy, even in the Transbay Tube, and has much higher peak operating speeds than many other systems in the country.

[28] BART also announced that the new train cars expected to enter service in December 2016 (see below) will be quieter, thanks to "'micro-plug' doors [that] help seal out noise".

The car had been removed from service in 2014, by which time it had run two million miles (3,200,000 km) and was held in reserve for spare parts.

The C2 cars had a multitude of issues including HVAC units that were the most likely in the fleet to break down, passenger doors that would often come off their tracks, and operator cabs with windows that would frequently fail and windshield wipers that would become stuck.

[35] Due to reduced ridership in the wake of the COVID-19 pandemic in the United States, full-length trains did not typically fill up, so BART chose to retire the legacy fleet and operate shorter trains with the intention of cutting costs and improving user experience.

Planned reuses include a short-term rental, bars, and a training facility for firefighters in Hayward.

While systems such as the Chicago Transit Authority and New York City Transit Authority have retained some retired railcars as part of a "heritage fleet" that operates on charters and special occasions, BART has stated such a fleet would not be feasible due to the cars' incompatibility with the newer CBTC system, as well as limited yard space to store them and the obsolete components needed to maintain them.

[54] A major difference is an extra set of doorways on each side of the new cars to speed up boarding and alighting.

[56] Due to potential access issues for people with disabilities, the pilot car layout was modified by the BART board in February 2015 to include two wheelchair spaces in the center of the car, as well as alternative layouts for bike and flexible open spaces.

[62] After only running on the Orange Line since January, a set of D and E cars began transbay service in October 2018.

[63] In November 2018, BART announced they had negotiated to extend their purchase options to a total of 1,200 cars,[64] though reports in 2019 stated that this deal was still not final.

In June 2019, with 84 total cars delivered, Bombardier announced it would be moving production from their New York-based plant to a new facility shared with Hitachi Rail in Pittsburg, California in the East Bay.

[18] In January 2021, BART stopped accepting new cars pending reliability improvements to be made by Bombardier.

[65] That same month, the struggling Bombardier sold its transportation division to Alstom, which said it would work to recover operations.

Before the Alstom deal, the company had seen declining profits largely caused by a series of major delays in delivering new fleets of trains (including the Flexity streetcars for Toronto and R179 subway cars for New York City) and reliability problems once trains were placed in service.

[69] The Oakland Airport Connector uses a completely separate and independently operated fleet as it uses off-the-shelf cable-car-based automated guideway transit technology.