The Acela Express ( /əˈsɛlə/ ə-SEL-ə; 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 Baltimore, Philadelphia, and New York City. It uses tilting technology which allows the train to travel at higher speeds on the sharply curved NEC without disturbing passengers, by lowering lateral centrifugal forces, based on the concept of banked turns.
Acela Express trains are the only true high-speed trainsets in North America; the highest speed they attain is 150 mph (240 km/h), though their average is less than half that speed. The Acela has become popular with business travelers, and by some reckoning has captured over half of the market share of air or train travelers between Washington and New York. Between New York and Boston the Acela Express has up to a 54% share of the combined train and air market.
The Acela carried 3.2 million passengers in fiscal year 2010; the busiest Amtrak route is the somewhat slower Northeast Regional, which had 7.1 million riders in 2010 due to its lower fares and greater number of stops. The Acela Express is one of the few Amtrak lines to operate at a profit; the two train lines generate more than half of Amtrak's total revenue. In 2010, the Acela Express had a total revenue of US$440,119,294, up from $409,251,483 in 2009.