A Metro-North station in the Bronx (photo by dpriddy via flickr)

More Bronx residents are commuting to northern suburbs for work -- and the health care industry is what's drawing them.

William Wheeler, the director of special project development and planning at the New York MTA, said 235 trains serve the Bronx's 13 Metro-North stations each weekday -- and more are needed.

"Approximately 8.1 million rides were taken to and from Bronx stations last year," said Wheeler. "That’s a threefold increase since 1985."  About two-thirds of these riders start their rides in the Bronx and travel to points north: places like White Plains, Stamford, and Greenwich.

"This is the largest reverse commute market that we know of in the United States," he said, "and it’s grown 150% since 1990."

Wheeler made the comments Tuesday morning at a New York City Council hearing on transportation in the outer boroughs. (A video of the hearing is available here.)

"One of the major factors that generates a lot of that travel is health care employment," he said. "And I'm not just talking about hospital complexes and medical facilities, but elder care and other services that are directly related to health care."

The MTA is studying adding four Metro-North stations in the Bronx, at Co-op City, Morris Park, Parkchester and Hunts Point. But capacity for that service likely won't be possible until East Side Access is completed, bringing some Long Island Rail Road trains to Grand Central -- theoretically freeing up space at Penn Station for Bronx-bound trains.