Debbie Hersman of the National Transportation Safety Board said the emergency brake, known as the "mushroom," was depressed, and the steel rails showed evidence that the brakes were engaged. Investigators also said the striking train was in automatic mode, which means onboard computers should have controlled its speed and stopped it before it got too close to the stationary train.
In addition, Metro sources said, the first two cars of that train were two months overdue for scheduled maintenance of their braking systems.
Taken together, experts say these facts point to several possible scenarios: the operator activated the brake too late; the computers that are supposed to stop a train from getting too close to another train faltered; the train's brakes failed; or some combination of those. Some passengers on the striking train have said that they never felt the train slow down.
A team of NTSB investigators painstakingly searched through the tangled heap of metal on the tracks just north of the Fort Totten Station in Northeast Washington. They were examining everything: the condition of the trains, track and signals; the actions of the operator and her downtown supervisors; and the computers that control train movement and are supposed to automatically prevent crashes. Investigators will also look at maintenance work performed this month on the computerized train control system along the stretch of track where the crash took place.
Officials began to remove the cars from the trains yesterday and plan to try to experiment with similar trains to determine approximate speed and stopping distance, Hersman said. Service on the Red Line will continue to be disrupted while the investigation proceeds.
The crash, the force of which vaulted the striking train atop the train it rammed, occurred on a curve where the speed limit is 59 mph, Hersman said. Today's experiment will also try to determine whether the curve, or anything else, obstructed the train operator's view of the stopped train. The operator, Jeanice McMillan, 42, was among those who died in the accident. Investigators will examine her cellphone and text-messaging records, review her work and rest schedule and analyze blood samples, all standard NTSB procedures.
Investigators are also delving into the automatic train protection system, which is designed to make collisions impossible. Had the system been working correctly, it would have sensed that Train 112 was getting too close to Train 214 and automatically directed the brakes aboard McMillan's Train 112 to engage.
"I truly believe Metro is a safe system," Metro General Manager John B. Catoe Jr. said. Catoe said it was too early in the investigation to know what caused the crash, but he said there was "no evidence" that the operator was using a cellphone or texting at the time of the crash. After a special board meeting yesterday, he told reporters, "there's not a letter of evidence" to indicate operator error. And right now, he said, there is also no indication of signal failure.
The six cars that comprised Train 112 were put together in an unusual way. Metro trains operate in married pairs of rail cars and the lead car is almost always an "A" car, which some operators say run more smoothly and communicate better with the electronic devices buried along the track. But in the case of Train 112, the lead car was a "B" car, Metro officials said. It was unclear last night why the train was configured that way. It's also unclear what affect, if any, the configuration could have had on the crash.
The cars were among the oldest in Metro's fleet, purchased between 1974 and 1978 from Rohr Industries for the opening of the subway system. They have been rehabilitated and retrofitted "to keep them in good condition," said Metro Board Chairman Jim Graham of the District.
But federal investigators consider the cars to be unsafe because of a tendency during a crash to collapse into one another like a telescope, reducing the "survivability" space, or the area in a rail car in which passengers can escape harm.
Investigators are also delving into the automatic train protection system, which is designed to make collisions impossible. Had the system been working correctly, it would have sensed that Train 112 was getting too close to Train 214 and automatically directed the brakes aboard McMillan's Train 112 to engage.
"I truly believe Metro is a safe system," Metro General Manager John B. Catoe Jr. said. Catoe said it was too early in the investigation to know what caused the crash, but he said there was "no evidence" that the operator was using a cellphone or texting at the time of the crash. After a special board meeting yesterday, he told reporters, "there's not a letter of evidence" to indicate operator error. And right now, he said, there is also no indication of signal failure.
The six cars that comprised Train 112 were put together in an unusual way. Metro trains operate in married pairs of rail cars and the lead car is almost always an "A" car, which some operators say run more smoothly and communicate better with the electronic devices buried along the track. But in the case of Train 112, the lead car was a "B" car, Metro officials said. It was unclear last night why the train was configured that way. It's also unclear what affect, if any, the configuration could have had on the crash.
The cars were among the oldest in Metro's fleet, purchased between 1974 and 1978 from Rohr Industries for the opening of the subway system. They have been rehabilitated and retrofitted "to keep them in good condition," said Metro Board Chairman Jim Graham of the District.
But federal investigators consider the cars to be unsafe because of a tendency during a crash to collapse into one another like a telescope, reducing the "survivability" space, or the area in a rail car in which passengers can escape harm.
After a Rohr train telescoped during a 2004 crash at the Woodley Park-Zoo/Adams Morgan Station, the NTSB recommended that Metro retire the Rohrs or strengthen their frames to prevent collapse. But the transit agency refused, saying that the cars make up one-third of the fleet and that Metro could not afford to mothball them ahead of their planned retirement in 2012, and that retrofitting would be both costly and impractical. The NTSB, which makes safety recommendations but has no enforcement authority, disagreed with Metro's stance, calling it "unacceptable" at the time.
Yesterday, Hersman again questioned the safety of the Rohr cars and blamed Metro for failing to act. "We recommended to [Metro] to either retrofit those cars or phase them out of service," she said. "Those concerns were not addressed."
Metro still uses 290 1000 series rail cars, which make up more than 25 percent of its 1,126-car fleet
Graham said replacing the cars would cost almost $1 billion, money that Metro does not have. Metro is the only major transit system in the country without a source of dedicated funds. The agency appeals every year to the District, Virginia and Maryland for funding, a situation that makes long-term planning difficult.
The NTSB also recommended that Metro install data recorders, similar to the black boxes found in airplanes, in all of its rail cars after the 2004 crash. While the agency installed recorders in some of its newest cars, the Rohr cars did not have them -- a condition that Hersman also called unacceptable.
Metro officials also did not install critical software revisions that would have allowed investigators to determine whether the operator had applied the emergency brakes, and the train's speed during braking, according to a source knowledgeable about the braking systems. Investigators might be able to determine whether the emergency brakes were deployed based on physical evidence.
Metro's automated system is built around electronic relays on the trains and buried along the track that allow onboard computers to control speeds and stop trains from getting too close to one another. Over the past decade, Metro has struggled with troublesome relays. The agency tore out all 20,000 trackside relays in 1999 after discovering that a small portion designed to last 70 years were failing after 25.
The manufacturer, Alstom Signaling, agreed to replace the relays at a cost to Metro of about $8 million. None of the new relays have failed to date, one Metro official said.
The NTSB and the Federal Transit Administration have criticized Metro for failing to act aggressively to address safety problems, especially at the time of a 1996 crash at Shady Grove that killed a train operator.