A commuter rail line between Missouri City and the Texas Medical Center ­- comatose for nearly four years - has leapt back to life, even if the dollars needed to build it remain elusive.

Metropolitan Transit Authority board members on Thursday approved a resolution authorizing transit officials to "place" the project in the "Federal Transit Administration process" and look for ways to pay for it. When officials essentially placed the project on inactive status in September 2012 after spending $1 million on feasibility studies, it was estimated to cost about $400 million to build the rail line.

Board members stressed restarting the project was not tacit approval of it, or a promise for a single dollar toward building it.

"I just want to make sure we are clear," Metro board member Cindy Siegel said. "This is to allow the possibility of federal funding, but isn't a commitment."

Since voters approved the project in 2003, plans for a train line along U.S. 90A from south Gessner Road to Metro's Fannin South rail station south of Loop 610 have been the exception among Houston's contentious rail plans. For example, unlike intense opposition to a proposed rail line on Richmond Avenue that has been a point of contention among lawmakers, the 90A project enjoys robust support from Houston officials, elected officials in smaller cities and the area's congressional delegation.

Rep. Al Green, D-Houston, who represents the southwest Houston area where the rail line would run, has long called it one of his district's top transportation priorities.

Rep. John Culberson, R-Houston, who has been a constant opponent of the Richmond rail project, last year said the 90A line should be Metro's first priority once it has sufficient money for rail projects. Culberson's office on Thursday did not respond to a reporter's request for comment.

Demand for the line has grown as traffic congestion has continued to make travel along U.S. 59 and U.S. 90A more time-consuming. More development in the area, such as plans for a University of Texas research center in southwest Houston, also has spurred more interest, Metro board member Jim Robinson said.

"I know they are extremely interested in having rail go by there and this is adjacent to that," Robinson said, of the planners of the UT center.

In reviving the dormant rail project, Metro chairwoman Carrin Patman said it was important to gauge support for it and move forward. Technically, as the project remains approved by voters from the 2003 referendum, Metro officials can talk to federal transit officials anytime about its prospects.

"I don't think it was absolutely necessary," Patman said of the fresh resolution, "but I wanted to involve the board in the decision. I wanted to make sure everybody was on the same page."

The vote, she said, was "a clear mandate for us to get back in the process."

How to pay for the project, Patman said, will be worked out later. "There is no financial commitment to this point," she said.

The 2003 referendum allowed Metro to borrow up to $640 million to build rail lines, which the agency exhausted extending the Red Line north of downtown and building the Purple and Green lines southeast and east of downtown. Should Metro want to borrow more, they'd have to go back to voters.

At this point, Patman said she wasn't certain that would be necessary. All funding options for a 90A rail line, including public-private partnerships, would be considered, she said.

"I would not want to be limited," she said, citing the benefit of reopening discussions with federal officials. "We'll at least be in a position to avail ourselves."

Whenever the money materializes, it would still be years before riders could hop aboard. When Metro stopped preliminary planning a few years ago, officials estimated it would be five years before construction of the rail line began.

Also unresolved is how much of that earlier study is still valid. Metro CEO Tom Lambert said one of the first steps in restarting discussions with federal officials is assessing what previous plans are still usable.

"That's part of the process," he said.