Metro restored normal service by 3 p.m. on the Red Line following single-tracking between Medical Center and Grosvenor due to repairs to a circuit.
A circuit near the Medical Center Metro Station overheated about 7:20 a.m.
A WMATA official explained on Twitter that the overheated circuit prevented them from automating the train's route.
Metro put four trains on the single line during the morning rush to help ease delays.
During the morning commute, WMATA warned of delays of 20 to 30 minutes.
Passengers News4's Tony Tull spoke with weren't that upset with the delays, praising Metro for having representatives at each station to explain what was going on.
But Metro riders weren't the only commuters to see significant delays as they made their way to work Monday morning.
A jackknifed tractor-trailer shut down the Inner Loop between Connecticut and Georgia avenues around 3 a.m. Monday. Drivers were urged to avoid the area as sand trucks cleaned up leaking fuel.
The lanes were closed for just over three hours, opening up at about 6:10 a.m.