Investigators searching through the twisted, charred remains of the Silver Spring train crash are focusing on signal switch problems or human error to explain why a MARC commuter train was traveling twice as fast as it should have been before the two trains collided.
With half of the checks already completed on the signals, investigators say they are beginning to believe that a mistake by the MARC train operators may be to blame for the horrific accident.
"The facts are driving us toward the human," said John Goglia, a member of the National Transportation Safety Board who is leading the probe. "It can turn on a dime, but right know, actual evidence is pointing us toward human" error.
MARC Train 286 passed what was supposed to be a yellow signal and barreled through a crossing called Georgetown Junction about three miles later Friday night. Instead of rolling through the junction at 30 mph, the MARC train reached 63 mph before the engineer apparently spotted the oncoming Amtrak passenger train and slammed on his brakes.
Fifteen seconds later, the MARC skidded into the Amtrak, killing 11, injuring another 26 and creating a surreal scene of horribly burned bodies trapped in hulks of blackened steel. It could be weeks before investigators know exactly what went wrong on the tracks just outside of Washington.
Investigators are focusing their attention on the placement of the signal and whether the MARC engineers missed it or forgot they had seen it. The signal is 885 feet before the Kensington station. That means crew members should have seen the signal before stopping at the station and then traveled nearly three miles before the two trains collided.
For some reason, the crew sped from the station instead of rolling out at 30 mph, an indication that they either didn't see a yellow signal or may have forgotten. Investigators say they aren't sure yet how much time elapsed between the time the signal was supposedly switched on and the crash. But they say they are troubled that a signal had been placed before the station, not after it.
"We want to know why the hell they did that," Mr. Goglia said.
Fifteen federal investigators, assisted by outside experts, are examining the crash site. The 65 investigators have split into eight teams to examine everything from the tracks and the trains, to the signals, the data recorders and what human factors could have played a role.
Among the findings so far:
* Some exits on the MARC train malfunctioned. Although investigators say some doors and windows didn't open, they are unsure whether the malfunctions contributed to any injuries or deaths on the train.
* An Amtrak fuel tank that exploded could have contributed to the deaths of some passengers. Autopsies show that some died from effects of the fire and injuries from the crash, and that most of the victims were severely burned.
* Toxicology reports showing whether any of the MARC engineers was under the influence at the time of the crash should be completed this week. The dispatcher who says he switched the signal will not be tested because he was not deemed as being directly involved in the crash.
* Investigators say the snowy weather didn't play a role in the accident. They have also ruled that the tracks and the brakes on the trains are not to blame.
The trains collided about 5:30 p.m. about eight miles north of Union Station. The MARC train originated in Brunswick in Frederick County and was headed to Washington. Among the passengers were 18 Job Corps students returning from West Virginia.
The Amtrak train had just left Union Station, an hour behind schedule. It was heading west on its way to Chicago when a dispatcher routed it onto the same track as the MARC train so the Amtrak train could pass a slow-moving CSX freighter.
Before the Amtrak train could cross back over to a parallel set of tracks, the MARC train came racing through the junction. The MARC engineer slammed on his brakes, slowing the train from 63 mph to 41 mph within 15 seconds before the trains collided.
The MARC engineer was "very familiar" with the run, investigators said. In fact, the engineer made the same run the day before. But investigators say nearly $10 million worth of track and signal improvements have been made in that area in recent years.
They are reviewing blueprints of the work for clues to the accident.
What has caught their attention is the signal. It should have been switched to yellow, warning the MARC engineer to slow to 30 mph while dispatchers rerouted the Amtrak passenger train around the freight train.
Investigators are examining at least three theories to explain what happened:
* Either the signal was never switched to yellow from a command center that controls tracks and switches around the nation from Jacksonville, Fla.
* The engineer somehow failed to see the signal and didn't realize his mistake until 15 seconds before the accident, when he saw the Amtrak train and slammed on the brakes.
* The engineer saw the signal, but somehow forgot.
The last theory is receiving plenty of attention.
As the MARC train pulled into the Kensington station, the engineer confirmed that he had seen a signal. In a routine confirmation procedure, the engineer noted the signal, and investigators believe another worker repeated the confirmation.
The confirmation was picked up by members of at least one other train crew in the area, who heard the transmission on a hand-held radio. Investigators interviewed the MARC crew members, but none could remember what color signal the engineer confirmed.
Investigators say they are searching for other crews that might have heard the transmission.
Mr. Goglia said he doesn't know why a signal was never placed after the Kensington station.
"That's a good question," he said. "I'm going to be asking the same question myself."