“As of 3:30 p.m., Metro is in the process of removing 4000-series cars from its mainline tracks.”

Photo by PoPville flickr user Julian Ortiz

From WMATA:

“Metro to remove 4000-series railcars after safety concern identified

Metro General Manager/CEO Paul J. Wiedefeld today ordered the immediate removal from service of all 4000-series railcars following the identification of a potential safety concern involving the train’s automatic train control (ATC) system that could result in a “false indication” to a train operator going undetected.

Metro’s ATC system keeps trains properly spaced and a safe distance from other trains by displaying “speed commands” on a control panel in the operator’s cab. When operating in “manual mode,” the train operator responds to the speed commands, which indicate the train’s maximum authorized speed relative to the train’s location and distance from other trains. Train operators receive “zero speed commands” — indicated by a double zero — when the train is not authorized to move (i.e. the equivalent of a “stop signal”).

Albeit remote, Metro railcar engineers believe the potential exists for an undetectable failure of the 4000-series ATC system control board that could result in improper speed commands being given to a train when a 4000-series car is in the lead position.

“Today’s action is being taken in an abundance of caution and, while we believe that the risk is small, it is a risk I am unwilling to take,” Wiedefeld said. “Everything we do here is going to put safety first, no matter what.”

As of 3:30 p.m., Metro is in the process of removing 4000-series cars from its mainline tracks. The process is expected to take several hours.

Based on a preliminary investigation initiated today, it appears that the 4000-series railcar manufacturer recommends annual testing as a way to mitigate the risk of a false indication. Such testing is not currently done at Metro.

Metro may consider “bellying” 4000-series cars in the center of trains — similar to 1000-series cars — at a future date. The ATC issue identified today is not a risk when the 4000-series cars are not in the lead position.

The 4000-series is the smallest and least reliable of Metro’s six “legacy” fleets. There are 41 married pairs of 4000-series cars currently in active service, andMetro was already considering retiring all of them by the end of 2017. Metro may further accelerate the 4000-series retirement in light of this newly identified issue.

Customers may notice fewer 8-car trains in service over the next several days as a result of today’s action.”