WASHINGTON (AFP) — The driver of a Washington metro train that slammed into the back of another subway train this week, killing nine people, appears to have braked heavily before impact, an ongoing probe into the accident showed Thursday.
"Investigators found metal-to-metal compression streak marks on both rails of the track for about 125 feet ending near the approximate point of impact, consistent with heavy braking," the National Transportation Safety Board (NTSB) said in a statement.
Earlier reports from the NTSB have also indicated that the driver of the striking train, 42-year-old Jeanice McMillan, tried in vain to stop her train from plowing into the back of a train that had stopped between stations during Monday's evening rush hour accident.
There was "some blueing of the rails approximately 300-400 feet prior to the point of collision," NTSB board official Deborah Hersman told a news conference on Wednesday.
"Blueing indicates that there was some emergency braking that might have taken place," she added.
Still more probe results have shown that the emergency brake on the train McMillan was operating had been depressed.
McMillan was killed in the crash, which severely compacted the front car of her train, leaving portions of it disintegrated.
The train she was operating was forced by the impact of the crash up onto the back of the other train, which was shoved forward seven feet (two meters) by the force of the crash.
The operator of the struck train told NTSB investigators who interviewed him Thursday that he had stopped between stations on his way into Washington after seeing a train in front of him.
"While stopped, he said that he felt a hard push from behind," the safety board said.
Officials have begun inspecting all 3,000 signaling circuits, located beneath train tracks and in control rooms, on the Washington Metro system, general manager John Catoe said after NTSB experts said their probe had turned up "anomalies" in a circuit on the stretch of track where the crash occurred.
Circuits send speed commands to trains and tell them when to stop or proceed.
In tests conducted overnight at the accident site, investigators used a simulator train to see what commands the faulty circuit would send "when there's a train standing in that circuit," said Hersman.
The tests showed that "the circuits lost detection" of a train that was stopped at the same location as the struck train in Monday's evening rush hour accident, the NTSB said Thursday.
The driver of the struck train told the NTSB experts that he was operating his train in manual mode. It is believed that McMillan was operating in automatic mode, which is standard procedure during rush hour in Washington's Metro system.
"Whether trains are operating in automatic or manual, these circuits are vital," Hersman said.
"They are going to be providing information and feedback to the operators of the train and to the trains themselves when they're in automatic," she said.
Investigators were examining data retrieved from information recorders on the struck train, but the older, 1,000-series train driven by McMillan did not have onboard accident data recorders, the NTSB said.
The NTSB has recommended that these older trains be either retrofitted to make them more crash-resistant or removed from service altogether.
According to a statement issued by Metro Thursday, rehabilitating the 1,000-series cars was "not practical because the modification could result in more injuries."
Replacing the 300 1,000-series cars still in service in Washington's subway train system would cost around one billion dollars, Catoe said, adding that Metro was "in pursuit of the funding to make that happen."
No results were available from "bench-tests" the NTSB said it was going to conduct Thursday to see if two electronic brake control units (EBCUs) which were extricated from the mangled wreckage of the first two cars of the train operated by McMillan were working correctly.
The EBCUs taken from the last four cars of the six-car train had no defects, the NTSB said after reviewing them.
The "anti-climbers" -- extensions on trains that function like a combination of bumper and shield and are supposed to prevent one train riding up onto the other on impact -- had engaged both on the front car of the striking train and on the rear car of the struck train, the probe has shown.
"But the car body failed to stay intact when those anti-climbers engaged, and it climbed up the struck train," said Hersman.
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