The No. 1 reverse-commute market in the U.S. is in the Bronx, an MTA official said Tuesday.

Passengers took about 8.1 million rides to and from Bronx stations on Metro-North last year, and about two-thirds travel to points north: places like White Plains, Stamford, and Greenwich, according to William Wheeler, the director of special project development and planning at the MTA.

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

 He added, "One of the major factors that generates a lot of that travel is health care employment."

He said 235 trains serve the 13 Metro-North stations in the Bronx — which has seen ridership increase threefold increase since 1995

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

The MTA is studying (PDF) 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.