The National Transportation Safety Board is warning all subways and Metro rail tunnels to inspect their overbore wheel rails this month as part of a growing rash of defective failures on the nation’s rails.
The alert issued Tuesday comes after a chunk of steel fell from a subway car on Monday on the C subway line in Brooklyn, injuring four passengers, and after three railballast incidents in New York this month.
The Federal Railroad Administration said Wednesday it had linked a piece of rubber in a concrete ballast to two of the three broken subways over the last month. FRA spokesman Rob Kulat said that the FRA would be working closely with the NTSB to determine if the subway failures were somehow related to design defects.
A total of four railballast failures have been reported across the nation, including in Los Angeles, Chicago and Tacoma, according to the National Transportation Safety Board. The string of failures has left railroads and subways scrambling to figure out the root causes of the failures.
“With subway rails, if a piece of metal should break off, it’s a very difficult engineering problem,” said Jonathan Adkins, the deputy chief of the Federal Railroad Administration’s Office of Research and Technology.
Adkins said he had not heard of a mechanism in place to indicate when a rail had broken off from a long and winding track, and said it could have taken many months before a FRA inspector investigated a broken ballast and was able to determine the cause.
“They’re in a really difficult position because they have to address it now,” Adkins said. “They’re not just telling you what happened, they have to go out and find out the cause of the failure.”
Richard Kuprewicz, an engineer with Accufacts, a consulting firm that specializes in rail transit issues, said that normally engineers would need to see evidence of external corrosion, be able to look at the track beneath the rail, and diagnose any anomalies with equipment.
Kuprewicz said he understood that a piece of rubber ballast was discovered to be present in the ballast that broke off of a rail, making the rail ballast unsafe.
But, he said, it may be “very difficult” to determine the cause and effect of the rubber ballast in a concrete ballast.
“Because rubber ballasts are usually slow-moving for their length, it’s like putting a nail in a piece of wood, which causes it to come apart,” Kuprewicz said. “Usually it takes quite a bit of time to find out which part broke.”
Adkins said he had not heard of any work being done on steel overbore wheels recently, but said it was possible for slabs of rock below tracks to cause wheels to malfunction.
In June, two subway cars on the No. 4 line in New York were taken out of service because of faulty railballs. A bike traveling on a subway track suffered a punctured eardrum after a car on the D line struck it while “dancing,” according to reports. And a truck and subway car on the C line collided in New York in May, blocking the tracks for three hours.
Metro officials said that last month, the transit agency shifted its overbore cars to reinforce ballast with abrasive filler made of cobalt-chrome.
BART, the third largest transit agency in the country, is using friction-resisting rubber ballasts on its trains and overhead wires to address a problem with already-knotted steel ballasts, according to an investigation by The Mercury News. After the failure of a single ballast to clear rail wheels, dozens of ballasts built up with no clear way to detangle them, BART safety officials told the newspaper.
The railballast failures come at a time when FRA inspector inspections are up to more than 8,000 trains and the NNSB has declined, according to the agency’s monthly report. In 2016, however, incidents involving damaged and worn or loose railballasts were down from a five-year average, Adkins said.
In a statement, FRA acting Secretary Sarah Feinberg told Bloomberg News that the agency was working with the NNSB to “determine what occurred and what measures need to be taken to prevent similar incidents in the future.”