The Bombardier–Alstom HHP-8 (High Horse Power 8000) is a type of twin-cab electric locomotive manufactured by a consortium of Bombardier Transportation and Alstom for Amtrak and MARC. The locomotive's electrical drive technology is directly derived from the SNCF BB 36000 manufactured by Alstom. A small class size and reliability problems with correspondingly high per capita maintenance and replacement costs led Amtrak to retire all of its HHP-8s after only a decade in service. MARC initially made the decision to retire their HHP-8s, but later opted to refurbish their fleet from 2017 to 2018. Background Amtrak assumed control of almost all private sector intercity passenger rail service in the United States on May 1, 1971. The centerpiece of Amtrak's system was the Northeast Corridor, a line between Washington, D.C. and Boston, Massachusetts, via New York City. The line was electrified from Washington through New York to New Haven, Connecticut; diesel locomotives handled trains over the remaining between New Haven and Boston. In the 1990s Amtrak rebuilt and electrified the route as part of the project which established high-speed Acela Express service between Washington and Boston. The elimination of diesel service between New Haven and Boston meant that Amtrak would need additional electric locomotives to pull conventional trains east of New Haven. Neither of Amtrak's existing designs, the EMD AEM-7 and GE E60, were still in production, and the latter was slated for retirement. Amtrak chose to have Bombardier and Alstom, makers of the Acela Express, produce a visually-similar derivative for conventional service. Design The HHP-8 measures long by wide and stands tall (from the rail to the locomotive roof, excluding the pantographs). This was longer than the AEM-7, though still shorter than the E60. The locomotive weighs . The carbody is stainless steel; the locomotive has a 6 MJ crash energy absorbance structure. Reflecting the varied electrification schemes on the Northeast Corridor the locomotives were designed to operate at three different voltages: 12 kV 25 Hz AC, 12.5 kV 60 Hz AC, and 25 kV 60 Hz AC. The electrical traction system is directly derived from the system used on Alstom's BB 36000 Astride locomotives; this includes four three phase asynchronous traction motors powered by GTO based inverters, with one inverter per motor; the electric system also allows regenerative and rheostatic braking. The locomotives were designed for up to operation but are actually limited in service to Federal Railroad Administration Tier