Hippo. Amtrak Train 97 (Silver Meteor) crosses Dock Bridge from Harrison to Newark, New Jersey over the Passaic River with HHP-8 AMTK 664 (Bombardier, 6/2000) leading on Sunday, November 27, 2011. The HHP-8 is a locomotive externally similar in design to the Acela power cars, but has an operating cab at each end. HHP-8 loosely stands for High HorsePower-8,000hp, but the name quickly lent itself to the nickname "hippo". The 15 HHP-8s that Amtrak leased lasted a little over a decade in service before being stored. They have since been renumbered from 650-664 to 680-694 to make room for the Siemens ACS-64 class on the roster.