4月4日，联邦政府为期延长的绿线扩展而点燃了新的估计成本结构。23亿美元的MBTA轻轨扩展计划于2021年底完成，包括七个新车站和两个新的分支机构，从东剑桥市的一个重新定位的Lechmere站到萨默维尔的Union Square和Medford的College Avenue。

The milestone comes almost a year after the project was revitalized when Massachusetts transportation officials decided to移动forwarda scaled-down version of the 4.5-mile extension. That move came after the project was iced for almost a year in 2015 when it was discovered that it was running nearly $1 billion over budget.

The federal government, which pledged $1 billion towards the original plan in 2014, still must approve the overall project.

“The administration, MassDOT and MBTA appreciate the Federal Transit Administration’s analysis and recognition of the work that was put into the GLX project's new design, timeline, cost estimates and risk review,” John Dalton, MBTA program manager for the project, said in a statement. “MassDOT and the MBTA look forward to continuing to work with our federal partners, while continuing to invest in the improvements and long-term infrastructure upgrades to the core system over one million riders depend on each day.”

The state says it will also fill a $64.3-million funding gap for the project with $32 million in “special obligation bonds” from its rail enhancement program, $28.3 million from the unallocated contingency for the Red and Orange Line infrastructure program and $4 million from two recently completed projects (the Salem Garage and Wachusett Extension) that came in under budget.

The MBTAshort listed three design-build teamsin February to compete for the project shortely after the Trump Administration put the Green Line Extension on a list of priority infrastructure projects in January.

The MBTA released a draft of its request for proposal to the short-listed teams last month.

Dalton, who was hired to run the project late last year, called the draft RFP "a major step in the ongoing procurement process" and added that it "reaffirms the primary objective of delivering the base scope of the program while also allowing for the inclusion of additive-scope options if the completive pricing received from the design-build teams will allow."

他说，合同的枪支团队应重点关注“核心要素 - 七个站和火车服务，然后再定价其他示波器要素，但不需要遵守该项目的成功完成。”

The T has identified “six additive options” that include platform canopies, additional elevators, public art, additional community connections and extensions to the community path that will run along the extension and an enhanced vehicle maintenance facility in Somerville.

The MBTA will release the final RFP after collecting feedback from the design-build teams on the draft RFP. The teams must submit their price proposals in September before contracts are award later in the fall.