Update: The signal problem was resolved just before 4:50 p.m., Metro reports. All trains are moving, but expect residual delays on the Red Line. Some trains will be offloaded and turned around to keep on schedule, so watch out for crowded platforms. 

Earlier: Red Line trains are delayed by at least 30 to 45 minutes due to a signal problem at Silver Spring, according to Metro. This is occurring just as the evening rush hour gets underway, which means that in addition to delays, riders should be ready for heavy crowding at stations along the Red Line. 

Metro riders should consider taking the Green Line or a Metrobus to avoid the Red Line if possible. 

The Thursday commute home is already going to be difficult for many, with the National Christmas Tree Lighting Ceremony expected to snarl traffic throughout downtown Washington