Metro’s older trains feature two sets of chains that cover the gap between rail cars. (AP Photo/Pablo Martinez Monsivais)

Metro officials say they are working “as expeditiously as possible” to retrofit the agency’s new 7000-series trains with an additional safety device to help protect blind people from falling between rail cars, but worry they will not be able to meet the year-end deadline set last week by federal regulators.

If Metro fails to meet the Dec. 31 deadline, the Federal Transit Administration said last week that hundreds of the new stainless steel railcars must be pulled from service. But in a letter sent Friday to the FTA, Metro officials warn that sidelining those railcars would result in a 26 percent reduction in service and would be “severely and acutely detrimental” for daily riders.

“The magnitude of the adverse impact to [Metro’s] riders and the entire Washington Metropolitan area as a result of FTA’s threat to ground a large part of [Metro’s] fleet cannot be overstated,” Chief Safety Officer Patrick Lavin said in the letter.

“We strongly disagree with the ultimatum,” he said.

Controversy over the simple safety features known as “between-car barriers” has been ongoing at Metro for more than two years. Metro’s older rail cars are outfitted with “chain barriers,” metal chains that are bolted to the end of each rail car and intended to stop people from falling in the gap between two cars. For Metro’s newest trains, designers opted for a new type of barrier, stiff rubber flaps that cover the space.

Metro General Manager Paul J. Wiedefeld said Thursday that the change was introduced so that workers would not need to physically detach the chains from the cars in the process of moving them around the railyard for repairs. Employees occasionally sustained slip-and-fall injuries while trying to unchain the cars in snow or ice, he said. The rubber barriers precluded the need for manual unchaining.

But after at least two people with visual impairments were reported to have fallen onto the tracks between 7000-series railcars, FTA officials and some disability-rights advocates have questioned the safety of the new design, and called for Metro to install the chain barriers.

Last week, FTA issued a letter demanding that Metro complete the retrofits within six months, or the  agency may withhold federal funding and force Metro to shelve all the 7000-series trains. FTA also said Metro cannot introduce new trains to the system if they are not outfitted with the chain barriers.

In Metro’s response to FTA, Lavin wrote that the agency is attempting to install new barriers as fast as possible. But the manufacturer of the 7000-series cars, Kawasaki Rail Car, cannot find a supplier to produce enough of the barriers in time to meet the deadline.

“[Metro] directed Kawasaki to expedite the schedule and exhaust all resources to find an alternate or additional [between-car barrier] supplier,” Lavin said. “While Kawasaki is continuing to research alternative suppliers, to date none have been located.”

Before FTA sent its letter last week imposing the Dec. 31 deadline, Metro’s timeline for retrofitting all the 7000-series cars would have them finishing the project by November 2019.

Lavin said he wants FTA to reconsider its year-end deadline.

Metro also continues to push back against FTA’s conclusion that the rubber barriers are inadequate.

Lavin pointed out that subway systems in Boston, New York, Chicago, Atlanta and Miami all lack a standard, universal design for the between-car barriers across their fleets — one of the criticisms made by FTA of Metro’s use of two different designs.

They pointed out that the rubber flaps had previously been approved by the FTA and the Tri-State Oversight Committee, and that Metro’s Accessibility Advisory Committee participated in the testing process.

Citing a May 25 incident in which a woman using a white cane fell onto the tracks, Lavin said that video surveillance footage showed that the woman did not use her cane to tap on the floor or the doorway before she walked forward and fell into the gap, suggesting that she failed to employ “universally-accepted protocol” for using her cane.

“Risks created by individuals will always exist, and WMATA cannot be held to account for all such incidents,” Lavin wrote.

Lavin also referenced a July 2016 incident, where a federal employee with severe visual impairment reported falling into the gap between two cars in an empty station and scrambling out moments before the train pulled out of the station.

Lavin’s letter suggests that Metro officials are not convinced the incident actually happened.

“WMATA investigated the incident and was only able to substantiate that the customer dropped his white cane on the roadway,” the letter said. “WMATA was not able to substantiate through eye witness testimony or otherwise that the customer fell on the roadway.”

David Kosub, the man involved in that incident, has said that he screamed for the help of a station employee after hoisting himself out of the track bed and crawling onto the platform. When the station manager arrived, Kosub told him that he had just fallen on the tracks, and asked for help retrieving his cane from the track bed.

According to Kosub, the station manager returned his cane, but suggested that he believed Kosub was joking about falling onto the tracks, and said it was not necessary to file a report. Later, Kosub called Metro to report the incident and requested surveillance footage from the station cameras, but was told that the platform cameras were broken.

On Thursday, Metro board chairman Jack Evans said the agency intends to add the chain barriers to the trains as quickly as possible, but pointed out that an Amtrak train he rode recently did not feature any guard or covering over the gap between the cars.

“Amtrak and some of the other train systems have the same issue that we do, but we’re under more scrutiny than everybody else, so we’re going to move as quickly as possible to address it,” Evans said.