The Metroliner built by Budd were high-speed electric multiple units which were ordered by the PRR for service on the Northeast Corridor between New York City, Philadelphia and Washington. Designed for a top speed of 150 mph or 241 km/h, one reached 164 mph or 264 km/h on a test run. However, the track conditions and issues with the trains themselves limited their top speed in service to 120 mph or 193 km/h. They were introduced into service after Penn Central was formed and soon Amtrak took over.

Each train is being combined out of pairs of two cars with one cab in each car. They are powered on all axles. Budd built 31 coaches with their electrical part from Westinghouse and a total power of 1,200 hp. Additionally, 20 snack cars and ten parlor cars were built with their electrical part from General Electric which had only 1,020 hp. It quickly became evident that these trains were unreliable and the cars with GE equipment had insufficient power to climb certain grades with the expected speed.

So Amtrak had to start costly rebuilding programs to make them fit for daily service. They were withdrawn from the Metroliner service in 1981 after the introduction of the AEM-7 locomotives which managed to match the Metroliner schedules. The locomotives hauled Amfleet coaches which were based on the design of the Metroliner EMUs. Later, some of the EMUs were rebuilt to Amfleet cab cars. The unrebuilt units were used for the Keystone Service until 1988.