MORE than a century ago, before the term “transit-oriented development” entered the urban-planning glossary, plenty of it was being built in Westchester: clusters of housing, shops and sometimes industrial buildings close to railroad stations.

Now, after decades in which proximity to a train station was the last thing on most developers’ priority lists, it has gained tremendously in importance. And Westchester and counties farther north are starting to emulate parts of Long Island and the New Jersey suburbs in reconfiguring downtown areas with more, and more densely built, places to live.

The real estate arm of Metro-North, in concert with three municipalities, is planning transit-oriented communities for Mount Vernon and Harrison, as well as a third for Poughkeepsie in Dutchess County. Similarly, two private companies are planning far larger transit-oriented developments, one on Route 22 in Dutchess and the other at the Harriman Metro-North station in Orange County.

In Harrison, Metro-North has received a number of responses to its request for development proposals, said Linda Corcoran, who oversees the railroad’s transit-oriented development program. The plan involves 3.3 acres with a parking garage, high-density residential development and retail stores. “It’s premature to estimate costs for the project,” Ms. Corcoran said, “but we’re dealing with a cooperative town board, and that’s a plus.”