The long-stalled Fenway Center project is finally pushing forward in earnest. Part of it, anyway.

Developer John Rosenthal was set to hold a public meeting Wednesday night on his plan for the five-building, mixed-use complex he has long envisioned above and along the Massachusetts Turnpike near Fenway Park. The meeting marks the start of formal review by the Boston Planning and Development Agency, with Rosenthal hoping to start construction next spring.

The project has been in the works for 14 years but has struggled even amid Boston’s hot real estate market, largely due to the cost of financing a large deck above the Mass. Pike and a commuter rail line.

Rosenthal and his development partner — Gerding Edlen of Portland Ore. — announced in June a plan to break construction into two stages, starting with two apartment buildings on firm ground that could help finance the costly deck.

Before work can start, though, that change needs the approval of BPDA and the Massachusetts Department of Transportation, which gave Rosenthal a 99-year-lease on the air rights. City officials have generally been supportive, and a MassDOT spokeswoman said that the agency likes the new plan.

“MassDOT is hopeful that the proposed changes to Fenway Center will help launch this important project forward,’’ the agency said in a statement. “By realigning the project phasing, it enables the $500 million development to get underway and start to deliver significant benefits to the Commonwealth and City of Boston.’’

The clock is ticking. Rosenthal has until the end of the year to nail down his lease with MassDOT. When that’s signed and the first phase begins, he’ll owe $20 million to the state, with another $20 million due if the second, more-complex, phase does not launch.

Rosenthal and his partners say they have raised $230 million in financing to start work on phase one. They hope that proceeds from the apartment buildings will help enable the second portion to begin construction in 2018 or 2019.

Tim Logan can be reached at tim.logan@globe.com. Follow him on Twitter at @bytimlogan.