DALLAS -- On Tuesday night, the DART Board agreed to financially roadmap two very big projects.

One project could potentially build the Cotton Belt line from Plano to DFW Airport. The second project involves a Dallas subway line through downtown, known as the D2.

DART tells News 8 that each project could cost around $1 billion apiece, with the caveat that the alignment and engineering have not been addressed for the subway project yet, which means its projections are fluid.

On Tuesday, DART spokesperson Morgan Lyons said the Cotton Belt line could cost just north of $1 billion, and the D2 slightly less than $1 billion.

There have been concerns from Dallas City Council members that the subway line was not as high a priority as the Cotton Belt line. This month, the Council unanimously said subway and streetcar expansions should take priority over the Cotton Belt. One council member even stated it's possible the subway line would be the first to be dropped, if all funding streams aren't realized.

Both projects are also dependent upon federal grants. The Coalition for a New Dallas, a new urbanism political action committee, has said that the large amount of debt required to build the Cotton Belt will make federal authorities look less favorably on DART’s overall finances and be less likely to increase the D2 grant.

DART’s proposed long-range plan relies on a new federal loan program to speed up construction on the Cotton Belt. Officials say that building the line sooner will help cut the overall price tag, since construction costs are expected to rise over time.

But the new $1.1 billion cost of the project also calls for most of the line to be built as a single set of tracks, something that will limit the number and frequency of trains that can run on the line.

If everything goes as planned, the Cotton Belt line would be complete in 2022 and the subway line in 2024.

Information from our media partners at The Texas Tribune was used in this report. Click here to read their earlier coverage on the DART vote.