Since the crash happened in an open area where the subway travels across the bridge, newspapers were covered in photos of the two silver subway cars dramatically smashed together and first responders attempting difficult rescues above the East River. A work train ahead of the 'M' Train had caused the delays, and the 'M' Train operator did not inform the command center of the train was stopped on the bridge. The 'M' Train would normally be exiting the bridge into Manhattan once the 'J' Train began crossing from Brooklyn.

The NTSB found that Layton Gibson, the 'J' Train operator, was not impaired by drugs or alcohol and he had performed normally and appeared alert during the rest of his work shift, so the investigation concluded that he was fatigued after an 8-hour overnight shift and from swinging from day work to night work, which made him overly tired and led to him missing yellow and red track signals showing that a train was stopped ahead and not engaging the emergency brake in time. In addition, the spacing between signals was too short for the failsafe emergency brake to stop the train.

An off-duty train operator and a conductor on the 'J' Train both recalled hearing the sound of the train's emergency brakes a few seconds before impact, but the train had no chance of stopping in such a short distance. A mechanical emergency system designed to stop the train if it passes a red signal seemed to have been properly tripped, but the distance between the emergency system and the stopped train was not long enough for the emergency brakes to stop the train. During a later inspection, the NTSB found evidence that the train was under full power when the emergency braking began and was traveling about 35 mph as it passed the second-to-last stop signal before the crash and about 17 mph when it hit the 'M' Train.

The collision occurred on the Brooklyn side of the Williamsburg Bridge, just before the first tower, on a section of subway infrastructure that had been installed in 1918.

You may not be familiar with the crash if you weren't in the city at the time, but it has affected nearly every subway ride thereafter: As a result of that collision and as a way of dealing with an aging signaling system, train speeds were lowered across the subway system, which only began to be lifted in January 2019 in an effort to relieve systemwide delays caused by low speed limits and improperly-adjusted signals that could mistakenly activate a train's emergency brakes. Prior to the 1995 crash, there were no speed restrictions at the bridge and the majority of subway trains didn't even have speedometers, so train operators were left to estimate the speed on their own.