A new Port Authority study could revive the debate over a No. 7 train subway extension across the Hudson River into the swamps of Secaucus.

The agency plans to release a study that argues extending the 7 train to New Jersey is “the one major trans-Hudson investment that studies suggest could significantly reduce long-term Bus Terminal demand,” according to sources cited by Politico.

The Port Authority is currently accepting proposals to redevelop its 8th Avenue bus terminal in Midtown Manhattan. But opponents of the plan argue that the agency would be better served constructing a smaller terminal in Manhattan as well as one on the New Jersey side of the river and connecting it to Manhattan via subway. RXR Realty’s Scott Rechler, a former Port Authority board member, is among the idea’s supporters.

A study commissioned in 2013 by the City of New York estimated that the 7 train to Secaucus would accommodate an additional 128,000 passengers a day.

But according to the Politico report, building a subway tunnel would cost billions and still wouldn’t eliminate the need for a new bus terminal in Manhattan, making it unlikely.

Observers told the politics website that a new subway tunnel and a new bus Manhattan bus terminal could be complementary. “One is going go to be pulling people in from farther away,” said Richard Barone of the Regional Plan Association. “The other one would be an urban transit service [with] just one, maybe two stops to New Jersey.” [Politico] — Konrad Putzier