During the 1974–75 delivery of the "Silverliner IV" cars from General Electric numbered PC 270–303, the Pioneers were renumbered 244–248 (the 249 had been wrecked and retired by that time) to form a solid block of MU's containing both the new cars and existing Silverliner II and III cars. After purchasing a number of push-pull trainsets and AEM7s in 1987, SEPTA found itself possessing a sufficient number of Silverliner II, III and IV MU cars to retire the Pioneer III/Silverliner I cars. Retirement finally came with the spring timetable change on April 1, 1990, due to a requirement by Amtrak that all locomotives and self-propelled railcars operating on the Northeast Corridor be equipped with a new type of train control, a result of a 1987 train collision. Until 2000, the cars were kept in storage near Wayne Junction. Although there were plans to convert the cars into locomotive-hauled coaches, SEPTA finally decided to dispose of the fleet due to the expense it would have taken to deal with PCBs in the transformers and the lack of ADA compliance. Of the 5 remaining Pioneer III/Silverliner I cars, three of the cars were sent to the AAR/FRA test site in Pueblo, Colorado, for use in crash tests, while the remaining two cars were donated to the Railroad Museum of Pennsylvania in Strasburg. The cars sent to the test site and the museum