The MBTA says a bad circuit board in the Orange Line's signaling system between Downtown Crossing and Oak Grove are to blame for delays in recent days - in which trains have been limited to 15 m.p.h. and manually directed between stations, with only one train allowed in either direction.
The T says the signals are now working between Downtown Crossing and North Station and expects to have the entire line back to normal operation by Sunday.
According to T spokesman Joe Pesaturo:
The MBTA's Signal Department found a defect in one of the electronic circuit boards used in the Orange Line Signal System from Downtown Crossing to Oak Grove. These boards are used in the control locations on this section of the Orange Line. The MBTA and the manufacturer of this equipment currently are implementing a corrective action plan. ... MBTA Signal staff is working around the clock at the remaining equipment locations that are still affected. As each location is cleared, the manual oversight will be replaced by [automatic train operation] and the delays will be reduced. We anticipate daily improvement until the corrective action plan is completed.