A vital safety system that keeps trains from colliding failed last week in the tunnel between Foggy Bottom and Rosslyn, forcing two quick-thinking train operators to manually stop their trains to avoid a crash, Metro officials said yesterday.
Until engineers figure out what caused the failure, transit managers have ordered all trains using the tunnel to operate manually, which is causing delays and crowding along the Blue and Orange lines during the afternoon commute.
Metro began running eight-car trains on the lines last night to ease the crowding, and officials said they will continue that practice until the problem is resolved and trains return to computerized operations.
"Until we can find the problem in the circuit and correct it, until we can replicate what happened so we can find the cause of it and fix it, we're running in manual," said Jim Hughes, Metro's acting deputy general manager for operations.
Metro's trains are run by onboard computers, which communicate with relays along the track bed and control train speed and braking. Another electronic system, called train separation, detects the position of trains and makes certain that a safe distance is maintained between them. That system forces a train to stop if it gets too close to another.
But about 6 p.m. last Tuesday, as Train 420 was heading from Foggy Bottom to Rosslyn, the operator of the following train noticed he was getting too close, Hughes said.
The operator of that train, No. 408, switched to manual controls and braked, Hughes said. When Train 408 came to a stop in the tunnel, the operator of a third train, No. 913, realized he was getting too close to Train 408 and also switched to manual to stop his train, Hughes said. Train 913, which had been traveling at 35 mph, came to rest in the dark tunnel about 50 feet from Train 408, he said.
That's when train controllers at Metro's downtown headquarters knew something was wrong with the track circuit that runs 1,000 feet between the Foggy Bottom and Rosslyn stations, Hughes said.
They halted all train traffic on the lines and ordered operators to run their trains manually through the affected stretch. Under manual operations, trains proceed one at a time through the mile-long stretch.
"It's a red-light effect," Hughes said. "Trains have to stop and wait their turn."
The restriction has added travel time to the Orange and Blue lines and has reduced the number of trains that can roll through the tunnel at Foggy Bottom from 28 an hour to about 23, creating crowding in stations during the evening rush.
Delays are more pronounced during the evening rush than the morning rush because Metro runs more Blue and Orange line trains in the evening.
The failure of the track circuit is highly unusual. Metro officials could not remember another instance when the train separation system did not perform, Hughes said. In tests late Tuesday, the circuit operated normally. But Hughes emphasized that trains will not return to computerized operations until Metro technicians and managers figure out what caused the failure and fix it.
Officials from Alstom Inc., the manufacturer of Metro's train control system, were scheduled to arrive today to assist Metro, Hughes said.
Several Metro riders have complained about a lack of information regarding delays. Hughes said the agency should have been faster to communicate the problem with passengers.