Sign up for our COVID-19 newsletter to stay up-to-date on the latest coronavirus news throughout New York City

Engineering gurus will begin studying a proposed billion-dollar passenger train that would run through southern Brooklyn, authorities announced on Wednesday.

The Metropolitan Transit Authority awarded infrastructure firm Aecom with a $1.3 million contract on Jan. 22 to determine the feasibility study for the project, which would revive passenger service on the Bay Ridge Branch — a freight line that once carried straphangers through Bay Ridge, Bensonhurst, Midwood, and East Flatbush until it was decommissioned in 1924.

The study will evaluate the potential for a subway, commuter rail, light rail or even a bus service for the line, all of which would operate in conjunction with existing and planned freight rail service, the MTA announced.

The passenger line would stretch from Brooklyn Army Terminal in Sunset Park to Astoria, Queens, and would connect to 11 existing subway stations along the way, providing transfers for 14 subway lines.

According to one urban planner, the train would play a pivotal role in linking transit-starved residents to subways and increasing accessibility within Brooklyn.

“Transit service on the Bay Ridge Line would not only provide better transit service between the outer boroughs, but also cut construction and acquisition costs since the rail tracks are already there,” said Tom Wright, the president and CEO of the nonprofit the Regional Plan Association.

The Bay Ridge Branch makes up about half of a longer line called the Triboro Line — a proposed passenger train that would continue past Astoria, up through the Bronx.

The Regional Plan Association has pushed for a study on the Triboro Line since the 1990s, and in June, support for the train ratcheted up when Assemblywoman Latrice Walker (D—Brownsville) proposed a bill calling on the Metropolitan Transit Authority to conduct a study for the project.

While passenger service on the Bay Ridge Branch has been defunct since the early 1900s, some urban planners argue that the freight line is well-suited for commission because its tracks are currently underutilized, and the existing infrastructure would help keep costs down relative to building new tunnels.

But the project’s astronomical costs make the Bay Ridge Branch line unlikely.

A senior analyst at the Regional Plan Association pegged the project’s price between $1 billion and $2 billion — a figure that would eat up a sizable chunk of the transit authority’s $5.7 billion budget for all Long Island Rail Road-related work in its 2020-2024 Capital Plan.

Another recent MTA study revealed that a similar proposal to restore passenger service along an existing Rockaway line would cost a jaw-dropping $6.8 billion — more than $6 billion more than originally estimated, the City reported.

An MTA spokesman did not say how long the Bay Ridge Branch study will take, but previous feasibility studies indicate that the project will likely take years.