Acela

 ( Amtrak Routes ) 

On March 9, 1999, Amtrak unveiled its plan for the Acela Express, a high-speed train on the Northeast Corridor between Washington, D.C., and Boston. Several changes were made to the corridor to make it suitable for higher-speed electric trains. The Northend Electrification Project extended existing electrification from New Haven, Connecticut, to Boston to complete the overhead power supply along the route, and several grade crossings were improved or removed. Prior to 2000, all trains bound for Boston had to switch to diesel power at New Haven.

A pilot trainset was completed by early 2000 and sent to Transportation Technology Center (TTC) for testing in June 2000. An inaugural VIP run of the Acela occurred on November 16, 2000, with the VIP train being led by power car number 2020 with no. 2009 at the opposite end, followed by the first revenue run on December 11, 2000, a few months after the intended date.

By 2011, the Acela fleet had reached half of its designed service life. Amtrak proposed several replacement options, including one as part of its A Vision for High-Speed Rail in the Northeast Corridor. In 2011, Amtrak announced that forty new Acela coaches would be ordered in 2012 to increase capacity on existing trainsets. The existing trains would have received two more coaches, lengthening the trainsets from a 1-6-1 configuration to 1-8-1 (power car—passenger cars—power car). The longer trainsets would have required the modifications of the Acela maintenance facilities in Boston, New York and Washington. The first of the stretched trainsets was to have entered service in fiscal year 2014. This plan was cancelled in 2012 in favor of replacing, rather than refurbishing, the Acela fleet.

In January 2014, Amtrak issued a request for proposals on 28 or more new model Acela trainsets, in a combined order with the California High-Speed Rail Authority. These bids were due May 17, 2014. After discussions with manufacturers, Amtrak and the California High Speed Rail Authority concluded their needs were too disparate for common rolling stock and decided not to pursue the joint option.

The Acela name was announced on March 9, 1999, as a part of the original announcement of the service itself. The branding team based the name " Acela" on the ideas of acceleration and excellence. At the same time, Amtrak launched what it called the Capstone Program, a short-lived plan to rebranding the NortheastDirect, Keystone Service and Empire Service trains as Acela Regional and the Clocker trains as Acela Commuter.

The Acela Regional name was first applied to NortheastDirect trains 130–133 on January 31, 2000. Those trains were the first electrified trains to run on the full Northeast Corridor between Washington, D.C., and Boston. As more trains were electrified, they too were rebranded.

Following mass rider confusion between the three services, the branding was removed from the lower-speed Acela Regional and Acela Commuter trains in 2003.

On September 23, 2019, Amtrak shortened the name of the service from Acela Express to simply Acela.Date and observation of train name change at Further examples of the dropping of "Express" on all press releases since then at "Media Room", Amtrak

At the same time, Amtrak introduced the Acela Nonstop, a direct train from Washington, D.C., to New York's Penn Station. The nonstop service was temporarily suspended as of March 10, 2020, due to low ridership caused by the COVID-19 pandemic.

The tilting carriages are based upon Bombardier's earlier LRC trains used on Via Rail rather than the TGV's non-tilting articulated trailers. Acela power cars and passenger cars are much heavier than those of the TGV in order to meet the FRA's crash standards. French and Canadian crews testing the Acela referred to it as "the pig" due to its weight. The extra weight leads to the Acela power-to-weight ratio being about 22.4 hp per tonne, compared to 30.8 hp for a SNCF TGV Reseau trainset. The Tier II crash standards, adopted in 1999, have also resulted in the passenger cars being designed without steps and trapdoors, which means that the trainsets can only serve lines with high-level platforms such as the Northeast Corridor. Acela trains are semi-permanently coupled (but not articulated as in the TGV) and are referred to as trainsets. Bombardier later used the Acela carriage design and a diesel engine/gas turbine variant of the power car for its experimental JetTrain.

The fleet expansion will allow for hourly New York–Boston service all day and half-hourly New York–Washington service at peak hours. The new trainsets will be longer, have 386 seats compared to 304 on Acela Express (a 27% increase) and will feature Tilting train technology that will initially allow service to operate at 160 mph (260 km/h) and would allow for service if proposed infrastructure improvements are completed.

The new trains were expected to be phased in between 2021 and 2022, after which the current fleet was to be retired. In December 2024, Amtrak updated the trainsets' announced release date to "Spring 2025", which was revised a second time to "coming soon" after the Spring season ended. , the new trains are still not in service.

The maximum speed limit on the Northeast Corridor is on of the route, in four sections of track in Rhode Island, Massachusetts, and New Jersey. The Acela achieves an average speed (including stops) of between Washington and New York, and an average speed of from New York to Boston. The average speed over the entire route is .

Speeds are limited by the route the corridor takes through urban areas, and there are several speed restrictions below over bridges or through tunnels that are over a century old. Altogether, Amtrak has identified 224 bridges along Acela route that are beyond their design life.

South of the Delaware River, the Acela's top speed is . One limiting factor is the Overhead line support system which was constructed before 1935 and lacks the constant-tension features of the new catenary east of New Haven. The Pennsylvania Railroad ran Metroliner test trains in the late 1960s as fast as and briefly intended to run the Metroliner service at speeds reaching . Certification testing for commercial operation at involving test runs at up to began between Trenton and New Brunswick in September 2012. Passenger operation at began in this region in late May 2022.

The fastest schedule between New York and Washington, DC, was 2 hours, 43 minutes in 2012. $450 million was allotted by President Barack Obama's administration to replace catenary and upgrade signals between Trenton and New Brunswick, which will allow speeds of over a stretch. The improvements were scheduled to be completed in 2016, but have been delayed; the project was partially completed in late May 2022, with the remainder projected in 2024. This section of track holds the record for the highest speed by a train in the US, which is , achieved in a test run by the U.S./Canada-built UAC TurboTrain on December 20, 1967.

North of New York City, Amtrak upgraded the track along the Connecticut shoreline east of New Haven to allow maximum speeds in excess of , in preparation for the Acela launch. Although this area contains the fastest current operating speeds (), it also has the slowest section of the NEC: between New Rochelle, New York, and New Haven, Connecticut. This section is owned by Metro-North Railroad and the Connecticut Department of Transportation and is heavily used by commuter trains which limit the speed of the Acela. Amtrak's trains achieve only on a limited stretch in New York State and rarely exceed at any time eastbound through Connecticut until reaching New Haven. This notes, on p.41, that the 90 mph section is from MP (mile post) 17.2 to MP 21.4; that begins midway between New Rochelle and Larchmont, and ends between Mamaroneck and Harrison. In 1992, ConnDOT began plans to upgrade the catenary system and replace outdated bridges on the New Haven Line to enable the Acela to run slightly faster. the catenary replacement and bridge work were under way and expected to be completed by mid-2018.

On July 9, 2007, Amtrak introduced a limited-stop round trip, with trains stopping only at Philadelphia between New York and Washington. This shortened the trip between the two cities to 2 hours 35 minutes, making the trip roughly an hour faster than some of the Northeast Regional train services. These trains were an experiment to find ways to expedite travel time on the Acela; Amtrak has since dropped them.

Tilting enables passengers to ride more comfortably on curved sections of track faster than would otherwise be possible, by leaning into the bend. Acela trainsets use active tilting above on most of the system, but some segments of track in the Northeast Corridor are too close together for the cars to safely tilt while maintaining FRA minimum space between trains on parallel tracks. Metro-North Railroad restricts tilting on the segment of track north of New York which it owns. The system was originally designed for a 6.8° tilt, but the cars were redesigned wider to accommodate wider seats and aisles that reduced allowable tilt to 4.2° to fit within the clearance constraints of the existing tracks. Traveling at higher than also requires constant-tension catenary, which is only implemented on the more modern catenary system north of New York City. South of New York City, the trains are restricted to . By comparison, the Northeast Regional and the now-defunct Metroliner service reached .

Acela service was originally expected to begin in late 1999 but was delayed. The catenary system could not support the intended speeds between Washington DC and New York City, but the newer system between New York City and Boston allows the higher speeds. Attention was drawn to the decreased 4.2° tilt, but this was not the root of the speed problem, as the tracks from New York to Boston are similar to those between New York and Washington, and the tilt mechanism is not the factor enabling higher speeds. Following repairs, the first Acela service began on December 11, 2000, a year behind schedule.

Acela travels between Boston and New York in about three and a half hours (an improvement of half an hour); New York to Washington runs take a minimum of two hours and forty-five minutes. These schedules, as well as the relative convenience of direct downtown-to-downtown rail service as opposed to air travel, especially after the September 11 attacks, have made the Acela Express more competitive with the . Due to this competition, Southwest Airlines canceled service between Washington and New York.

On April 15, 2005, the Acela was removed from service when cracks were found in the of many passenger coaches. The Bombardier-Alstom consortium replaced the discs under warranty. Limited service resumed in July 2005, as a portion of the fleet operated with new brake discs. Metroliner trains, which the Acela Express was intended to replace, filled in during the outage. Amtrak announced on September 21, 2005, that all 20 trainsets had been returned to full operation.

In October 2012, Acela service was cancelled immediately before, during, and after Hurricane Sandy, which damaged the North River Tunnels causing lasting delays and reliability problems.

In March 2020, all Acela trips were suspended as part of a round of service reduction in response to the COVID-19 pandemic in the United States. Amtrak resumed Acela service on June 1, 2020.