More than 12 hours after seven Amtrak rail cars careened off the tracks in Philadelphia into a twisted, mangled wreck — killing at least seven and injuring as many as 200 — the words spoken in the immediate aftermath by the city’s mayor still hold true.
“We do not know what happened here,” said Michael Nutter. “We do not know why it happened.”
National Transportation Safety Board member Robert Sumwalt, speaking alongside Nutter on Wednesday, said NTSB investigators will look at a number of factors in the accident, including “the track, the train signals, the operation of the train, the mechanical condition of the train, and human performance.”
“You have a lot of questions,” Sumwalt told reporters. “(And) we have a lot of questions.”
Here are some of the factors investigators will consider:
Speed
Whether Amtrak Northeast Regional Train 188 was traveling at an excessive speed is not yet known, but a source briefed by investigators said it is now believed that the train was traveling in excess of 100 mph — more than twice the speed it should have been going around a curve at Frankford Junction. The excessive speed theory jibes with what passenger Janna D’Ambrisi told CNN, about how she thought that the train was going “a little too fast around a curve.”
Trains, like airplanes, are equipped with event data recorders — better known as “black boxes” — that will officially determine its speed. Nutter said the train’s recorder was recovered Wednesday and sent to an Amtrak facility in Delaware, where its data is being downloaded. Information about that data could be made available later Wednesday, according to Sumwalt.
Track condition
Investigators will also consider the condition of the track. There are roughly 880,000 miles of rail track in the United States, according to Mary Schiavo, a former inspector general for the U.S. Department of Transportation and a CNN analyst, and a lot of it is in less-than-ideal shape. In Philadelphia, however, along the bustling Northeast corridor, the situation is perhaps more dire.
“It’s an extremely heavily used stretch of track,” Wald said of the area. “They have trouble keeping it in a state of good repair.”
Human error
Nutter told reporters the train’s engineer was injured in the crash, but has been able to speak to officials. It’s too early to determine if the engineer played any role here, but some recent rail accidents have been blamed on human error.
New York commuter train engineer William Rockefeller Jr. admitted falling asleep before derailing in a 2013 Bronx crash that left four dead and 67 injured, and investigators found that a 2009 trolley crash in Boston that injured more than 60 occurred because the operator was texting his girlfriend.
Collision with another train or vehicle
Nutter said there’s no indication that another train had anything to do with the derailment, and so far, no signs that a vehicle was involved either. The deadliest crash in the history of the New York commuter railroad occurred February 3 when a driver suddenly moved her SUV into the train’s path. The driver and five train passengers were killed.
The train’s mechanical condition
The locomotive — where the train’s engine is housed — flew off the tracks in such a manner that it was actually left standing upright. Whether or not mechanical failure played any role in the derailment has not yet been determined, but according to an official with the company that built it, that particular locomotive was practically brand new. A Siemens official told CNN that the high-speed electric passenger locomotive — one of 70 Amtrak ordered for service on the Northeast corridor — has only been in service since 2014.
Terrorism
A U.S. law enforcement official told CNN that so far, there is nothing to indicate the incident was an act of terrorism.
Weather conditions
According to CNN meteorologist Todd Borek, there were no weather-related conditions in the area that would have contributed to a crash. “No fog, no problems with visibility,” he said.
