Power problems caused severe delays on the MBTA's Blue, Green and Orange lines on Friday afternoon.
The MBTA said some sections of the three lines experienced delays of up to 25 minutes. Some trains had to hold at stations or operate under restricted speeds.
The power problems affected central subway portions of the system. The MBTA said the longest delays were on the Blue Line between the airport and Government Center, on the Orange Line between Downtown Crossing and North Station and on the Green Line between Copley and North Station.
Eastbound Green Line C and D trains terminated at Kenmore Station, with riders urged to use westbound B train service to Kenmore to transfer to the C and D train.
Later in the evening, MBTA Commuter Rail was reporting moderate to severe delays.
The MBTA said the outage stemmed from a cable problem at a substation in the North End.
The problems were first reported around 3 p.m. and power was restored to Park Station and the B and D branches of the Green Lines by 6 p.m. MBTA officials said they continued to work on full restoration of power on the Blue and Orange Lines.
T riders took to Twitter to vent their frustration about the delays.
"Hey @MBTA where should I submit for reimbursement for the Uber I had to take to get home??" one person said.
"I walked from Park to Prudential... beat the train by 20 minutes," said another.
"Throw the MBTA," said a third.