BOSTON (CBS) — The MBTA said repairs to “gradually restore” full service on the Red Line will take all summer. A train derailment at the JFK/UMass station on June 11 severely damaged the line’s signal system.

According to the MBTA, typical Red Line service involves 13 to 14 trains per hour. Following the derailment, six trains were running per hour. That has since been updated to 10 trains during rush hour.

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The MBTA expected the level of service to not change from six trains per hour and 10 trains per rush hour until the beginning of September.

“In order to safely operate trains at six-minute intervals, while also allowing crews to continue signal-system repairs, Red Line trains are passing through the JFK/UMass area under a carefully controlled manual operation. This complex process involves over 50 people at a given time to safely coordinate the movement of trains between the Red Line core and the Braintree and Ashmont branches,” said a statement from the MBTA.

General Manager Steven Poftak told reporters Friday, “We are working every day to decrease the amount of manual work that’s being done and if we are able [to make] sufficient progress, that number will decrease but I think to allow the riding public to plan, right now, we foresee this current level of service persisting at least through Labor Day.”

The derailment damaged hardware that controls the MBTA signal system (Photo credit: MBTA)

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Riders are still encouraged to give themselves extra 10-20 minutes of extra travel time.

“We understand how disruptive this has been for riders. Our priority really is on improving service but doing it as quickly as we can but doing it as safely as we can,” said Poftak.

“It is not a question of resources, it is a question of extensive damage to equipment that, in some cases, dates back to when this area was constructed, that’s a very complicated process to work through that and come up with fixes,” he added.

The cause of the derailment is still under investigation. Operator error and foul play have been ruled out.

After a Green Line derailment on June 8, the operator was determined to be at fault.

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The fleet of active Red Line trains were also inspected and no systematic issues were found, said Poftak.