General Manager/CEO Paul J. Wiedefeld of the Washington Metropolitan Area Transit Authority (Metro) has ordered the immediate removal from service of all 4000-series railcars from the lead position of trains due to the identification of a potential safety concern. The vehicle's automatic train control (ATC) system could result in a “false indication” to a train operator going undetected.
The ATC system keeps trains properly spaced at 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” when the train is not authorized to move.
Although it is a remote possibility, 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,” stated Wiedefeld. “Everything we do here is going to put safety first, no matter what.”
During a preliminary investigation, Metro found 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 since the ATC issue 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. Metro was already considering retiring all of them by the end of 2017 and may further accelerate the retirement in light of this issue.