As the truck pulled away from Greenbelt yard with car 4054, there was little of the nostalgia felt a year ago when Metro began retiring its original subway cars.

“There he goes,” Metro General Manager Paul J. Wiedefeld deadpanned, slipping in a wry quip. “It’s a very emotional moment.”

Metro’s 4000-series, riddled with problems in recent years and then deemed unworthy of a mid-life overhaul, reached the end of its life Wednesday as the agency began retiring the first of the fleet. The cars, which began arriving in 1991, were in service for a quarter-century, each logging about 1.5 million miles of travel in that time, costing about $1.3 million apiece.

The 100-car fleet arrived in time to supplement the initial portion of the Green Line, which opened in 1991. Through its lifespan, however, the fleet faced door, brake and propulsion issues, leading them to be pulled from service an unprecedented three times, according to the agency. The problems led 4000-series cars to be four times less reliable than the latest 7000-series model, according to one metric used by rail systems, the “mean distance between delays.”

Wiedefeld put it simply: “It’s the weakest link in the chain.”

The cars are less reliable, even, than the original model put into service when the system opened in 1976. That model, the 1000-series, was deemed un-“crashworthy” by the National Transportation Safety Board after the June 2009 Red Line crash at Fort Totten, and Metro prioritized their retirement. Metro said it had disposed of 136 of the 1000-series cars by the end of last year.

The agency aims to remove all 1000 and 4000-series cars from passenger service by the end of 2017.

The two models have forged an unlikely bond in recent years. Because of safety concerns, both 1000 and 4000-series models are required to be sandwiched between other, more reliable railcars. The move was made to allay passenger concerns about crashworthiness in the aftermath of the Fort Totten crash, which killed nine people. Late last year, Metro decided to “belly” 4000-series cars as well, after discovering problems which presented a collision risk.

4000-series cars in the lead position of a train are susceptible to receive improper speed commands, meaning they move when unauthorized to do so. Two years earlier, the cars were pulled from service after reports that doors were susceptible to opening mid-ride.

The fleet was also grounded in 2010 for the same door issue, but was put back into service when Metro said the problem was fixed.

The 4000-series models will be stripped of their Metro logos, radios and some reusable components, and sent to Baltimore for scrapping.