A "minor" derailment of an Amtrak Acela express train at the west end of New York's Penn Station resulted in a low-speed, sideswiping collision with an inbound NJ Transit train just after 9 a.m. on Friday, March 24, snarling traffic on all three railroads that use the at-capacity station for the rest of the day.  There were only a few injuries, all on the NJT train, and they were said to be minor. The outbound Acela was bound from Boston to Washington with about 250 passengers; the NJT train was inbound from Montclair State University and reportedly carried about 1000 commuters. Damage to the last two cars of the NJT train included scrape marks and pushed-in windows on the lowest level of the multi-level cars. The Amtrak train had not cleared the platform and its passengers were evacuated directly onto the station platform; similarly, the NJT train, which may have continued into the station, was emptied of its riders onto the platform.

The incident caused NJT and Amtrak traffic to be snarled for the rest of the day; NJT trains did not run for some time after the collision. Eventually, NJT established a modified schedule for the rest of the day, with inbound trains from the Northeast Corridor and North Jersey Coast line running once per hour; a special schedule was published for the outbound evening rush, with about 10 trains schedule to depart between 5 and 6 p.m. Midtown Direct service (on the Morristown, Gladstone, and Montclair-Boonton lines) was diverted to Hoboken, and NJT warned of delays in and out of Hoboken due to the additional traffic. Raritan Valley Line trains operated only to Newark. PATH trains to Hoboken were reported to be very crowded, as NJT passengers sought alternative routings.

The other two railroads using Penn Station were also affected.  The Long Island Rail Road said it was able to maintain more or less normal service until the evening rush hour approached, at which time it had to implement a severely restricted schedule, since half the tracks in uses in the peak hours were not available. Passengers were advised to use the line's Atlantic Terminal station in Brooklyn to avoid the Penn Station mess. 

Amtrak ran its usual Northeast Corridor services, subject to delay; but Keystone Service trains to and from Harrisburg were terminated at Newark. Empire Service trains to and from New York State operated only to Yonkers, where Metro-North shuttles conveyed passengers to and from Grand Central Terminal instead of New York Penn.

By Saturday NJT was saying that services were back to normal, except for New York - Rahway services which remained canceled, and by Monday (March 27) all carriers were reporting normal service.