A veteran transportation engineer who helped design the Metrorail system’s tracks says last week’s derailment may not have been preventable because track problems aren’t always visible to track inspectors and technicians.
“A [defect] may not have been big enough to warrant an action,” said Gus Ubaldi, a transportation engineering consultant who, in the 1970s, was part of the team that designed Metro’s track layout.
Ubaldi said that inspectors and technicians may not have been able to see if a problem with one of the rails posed a potential derailment hazard, and the stress of trains running over the problem area could have caused the rail to break without warning.
“If a rail breaks under a train, then that could cause a derailment; you can’t protect against that,” Ubaldi said.
Chief Safety Officer Pat Lavin of the Washington Metropolitan Area Transit Administration echoed Ubaldi’s sentiments, noting that “if you work in a transit industry, you recognize that no transit system is immune from the hazard of a broken rail – it is infrequent but not uncommon.”
Lavin said Jan. 16 Metro investigators are reviewing potential factors in the derailment including mechanical problems in the train, track and infrastructure and the train operator. Ubaldi listed the same three factors as Lavin as being necessary in a derailment investigation, calling the factors “derailment 101.”
Lavin noted that employees performed an ultrasonic test on the section of track where the train derailed Aug. 9. “The test indicated that no defects were found in area,” he said.
On Jan. 15, WMATA General Manager Paul Wiedefeld announced that results of a preliminary investigation into last week’s Red Line derailment indicate that a broken rail may have been a contributing factor, but cautioned that investigators had not yet determined a definitive cause.
Wiedefeld said that WMATA uses specialized train cars to test each section of track twice per year, and that the segment where the derailment occurred is scheduled for such testing, which uses ultrasonic vibrations to identify defects in the rails. The section where the derailment took place showed no defects during its last round of ultrasonic testing, which took place in August of last year.
Ubaldi suggested that a defect may have been present but undetected, and that it could have grown, and in doing so, caused the derailment.
Metro track walkers, who visually inspect tracks for defects, inspected that same section three times between New Year’s Day and the day of the derailment, WMATA Representative Sherry Ly explained, but “nothing was found” during those visual inspections. Metro’s inspection standards require that tracks be inspected twice within a seven-day period, Ly added.
Ubaldi said even if employees completed an ultrasound test of the track as late as December, results may not have raised any concerns to alert Metro before the Red Line train could derail.
The special testing cars “determine there are any internal defects in the rail that can cause it to break,” Ubaldi said. “Again, you can’t catch everything.”
As to the train, Lavin said employees transported the entire 7000 series train to the Brentwood Rail Yard for inspection “for any mechanical failures that could have contributed to this incident.”
Metro employees removed the section of track where the train derailed to have it tested for the investigation.
“The rail is being sent for forensic analysis including metallurgic testing by a qualified third party,” Lavin said.
Ubaldi said if the broken rail were a factor, investigators would need to determine whether the rail broke before the train drove over it or as the train was moving over it, and suggested that a damaged railcar wheel with a “flat spot” could have hit a pre-existing track defect and lead to a break in the rail.
However, Ubaldi wasn’t sure if the 7000 series wheels have developed any flat spots, but had a different suggestion: “Sometimes there might be an impact from the wheel from the train itself that causes a rail to break – there’s enough of an impact that causes the rail to snap.”
“I don’t know enough about 7000 series trains, but locomotives can, if you have wet rail for example, your wheel will slip just like your tires spin in the snow,” said Ubaldi, later adding, “It will generate heat and you can get a flat spot on the wheel.”
Investigators from the Federal Transit Administration, Metro’s acting state-level safety oversight agency, are investigating the derailment as well.
“FTA is providing oversight of WMATA’s investigation of the Red Line derailment to determine what occurred outside the Farragut North Metrorail station,” FTA representative Steven Kulm said. “The incident remains under investigation. FTA does not comment on ongoing investigations.”
“FTA is providing safety oversight of WMATA Metrorail operations until the Metrorail Safety Commission is established and a State Safety Oversight Program is certified for WMATA Metrorail,” he added.