The Acela Express ( ; colloquially abbreviated to Acela) is Amtrak's high-speed rail service along the Northeast Corridor (NEC) in the Northeast United States between Washington, D.C., and Boston via 14 intermediate stops including Baltimore, Philadelphia, and New York City. Acela Express trains are the fastest trainsets in the Americas; the highest speed they attain is in revenue service. Acela trains use tilting technology, which helps control lateral centrifugal forces, allowing the train to travel at higher speeds on the sharply curved NEC without disturbing passengers.