Photo courtesy of State House News Service.

After just more than one year managing the MBTA, Luis Ramirez is leaving the transit agency, and Transportation Secretary Stephanie Pollack said Tuesday she has chosen MBTA control board member Steve Poftak to take over in the new year.

Pollack said Poftak will start as MBTA general manager on Jan. 1 after she reached a “mutual agreement” with Ramirez for him to step aside. Ramirez’s departure comes just 15 months after he was chosen from a national pool of applicants to run the MBTA, and signed a three-year contract paying him $320,000 a year last year.

“Luis and I mutually agreed that the time was right for him to separate from the T,” Pollack said.

Ramirez’s departure takes effect immediately, and Deputy General Manager Jeff Gonneville will run the agency until Poftak can start the job next month.

Poftak has been the executive director of the Rappaport Institute for Greater Boston at the Harvard Kennedy School since 2012, and he has been the vice chair of the MBTA’s Fiscal Management and Control Board since 2015.

He has also sat on the MassDOT board of directors and briefly managed the MBTA during the nationwide search for a general manager that landed on Ramirez.

“He knows the organization, he knows the people and he knows the challenges the T faces and he’s going to hit the ground running,” Pollack said, describing Poftak as a “lifelong T rider.”

Pollack said the decision not to launch another search to replace Ramirez, and instead just appoint Poftak, was hers.

“We didn’t need a search. We didn’t need to find a national leader. We needed to find someone who could build on the first three and half years of work, so that was my call,” she said.

The secretary, who also made clear that she intends to stay on as secretary at the start of Gov. Charlie Baker’s second term, credited Ramirez with putting together the MBTA’s first balanced budget and accomplishing “a ton of internal work.”

“He’s accomplished a lot, but as we’ve been discussing the needs of the T in 2019 and beyond we mutually agreed that it was best for him to move on,” Pollack said.

Ramirez arrived in Boston from Texas where he has been a former General Electric executive and Dallas-based business consultant. Despite having no experience in the public transportation sector, he was hired as a turnaround artist who the administration considered capable of transforming the complex bureaucracy of the T.

The terms of Ramirez’s separation agreement were not immediately available.