Experts say that the causes include Metro’s practice of running more trains with more cars than it did in its early days. The additional weight puts more strain on the rails. The age of the system, parts of which began operation in the late 1970s, water leaks and poor maintenance could also be contributing to the problem.
The fact that workers operate trains manually, a practice begun for safety reasons following the 2009 Red Line crash, might also be a contributing factor.
Another possible reason for the cracking is “the stress put on the rail from the braking action of the trains — that wears at the rail,” said Matt Bassett, chairman of the Tri-State Oversight Committee, which monitors safety at Metro.
The transit authority has said it could be years before trains return to automatic control.
Metro chief spokesman Dan Stessel said it is unlikely that there is one conclusive cause.
“You can never say, ‘Aha. That’s it,’ ” he said. “It is probably a combo of things.” Metro is conducting metallurgical tests to “get better insight,” Stessel said.
In January, Metro had six cracked rails — the same number it had in January 2010. Passengers felt the pain of extensive delays when four of the incidents occurred during rush hour. Three of the incidents occurred on days when temperatures dipped from warm to very cold, causing rails to contract and pulling pieces apart, a problem common to rail systems, transit experts said.
What’s unique about the recent cracks, they said, is that four of the incidents occurred in tunnels — areas where rails don’t crack as often because they are protected from the elements.
Bassett said “there are more questions we need to ask,” given that some of the cracks occurred when temperatures were steady.
Most cracks have been discovered during routine checks by “track walkers” who visually walk and inspect tracks at least twice a week or a specialized machine that runs once every three months.
One crack was discovered by a train operator. Passengers aboard a train near Tenleytown station reported feeling a bump. Crews later confirmed a crack. Experts said the fact that a train operator found the crack is worrisome because it can mean that maintenance procedures have become lax.
“Ideally, their inspections should identify the problem areas,” Bassett said. But “depending on the cause of the underlying problem, they might not get any warning before the failure occurred.”
NTSB wants answers
The recent rail cracks have led the National Transportation Safety Board to ask for “additional information” on Metro’s findings to “determine if further action is required,” according to Keith Holloway, a spokesman for the NTSB.
Metro officials said they are taking effective measures to detect cracks. Of the 49 cracked rails found last year, 71 percent were identified in the inspection process — either by track walkers or specialized equipment, Stessel said. Thirteen were detected by signals that trigger when there is a disruption in the electrical current going through the rails. He was unsure how the remaining one was detected.
Stessel said many cracks are found at times when passengers are not affected.
“We’re detecting more of them, but the system is not getting any younger,” he said.
Rob Troup, assistant general manager of Metro’s rail infrastructure and engineering, said that Metro is still “looking for the commonality” in the incidents.
Troup said a number of issues could be at play, including weather, age and how the tracks wear. He said “everything on the Red Line is older,” which makes it “predisposed” to possibly having more cracks because the tracks are worn and tunnels can have water leaks that lead to cracks. That’s why, he said, “we are aggressively pursuing rail replacement on that line.”
Troup said that Metro has determined that the cracked rails are “not from the same batch,” which he said “tells us we don’t have any manufacturing defects.”
Imperfections in wheels can cause problems, too, said John Zuspan, president of Track Guy Consultants in Canonsburg, Penn., who worked on Metro’s tracks in the 1980s as a contractor. He compared a rail to a length of wire, bending back and forth.
“The force that’s applied [from a rail car] can turn a small, tiny crack into a bigger one,” he said. “Eventually, it can break from that small crack.”
Experts aren’t surprised
Other transit experts said that considering Metro’s age, cracked rails aren’t too surprising.
New York Transit, which has 673 miles of track, said it sees about 1.63 breaks per mile in its underground areas and 0.22 breaks per mile on outdoor parts.
A spokesman for Bay Area Rapid Transit, which operates 104 miles of track in the San Francisco Bay area, said it has had 10 or fewer cracked rails over the past three years because of extensive maintenance and the lack of extreme temperature changes.
Martin Schroeder, chief engineer for the American Public Transportation Association, said Metro’s six cracked rail incidents in a month isn’t too surprising “given the age, complexity and wear of the system.”
“They’re doing their utmost to find cracks and get them fixed,” Schroeder said. “It may look to riders like they’re not doing well, but given the fact they’re doing more preventable measures is some progress.”
In the past year, Metro has replaced nearly 15 miles of rail on the 106 miles of track in the system, 24,300 fasteners and 36 switches as part of its capital budget to try to fix the aging and deteriorating system.
The agency purchased a $14 million track geometry vehicle that will do ultrasonic and laser testing of rails an average of five nights a week. It is expected to be delivered in the spring.
“We’ll be able to manage these significantly better,” Troup said.