Among the far-reaching ambitions of Mayor Bill de Blasio’s OneNYC plan, one proposal stood out in the transportation world on Wednesday: the study of a new subway line along Utica Avenue in Brooklyn.

The concept is hardly new; it has been debated for at least a century, with no discernible results.

A 1910 article in The New York Times, under the headline “Transit Outlook Bright in Brooklyn,” said “a strong movement” was afoot to construct it. Another effort was made in 1928. More recently, an attempt in the 1970s failed after a City Council member from Brooklyn complained that the area did not have a large enough population to support the line.

Nonetheless, the de Blasio administration placed the concept back in the spotlight, suggesting that the area was a prime spot for expansion because it is one of the most crowded parts of the city without direct access to the subway.

The mayor’s request for the Metropolitan Transportation Authority to examine bringing No. 3 and 4 train service down from the Eastern Parkway branch, through East Flatbush, came as a surprise to many.