As a rail commuting center, Union Station doesn't come close to rivaling New York's Grand Central Station or Pennsylvania Station, but every day some 3,200 people arrive and depart there on Maryland commuter trains.

Come June 3, those folks can expect to pay 8 percent more for their monthly commutation tickets in what would be the first fare rise since 1981. The Maryland State Railroad Administration, part of the state Department of Transportation that subsidizes the rail fares, has posted the increase, subject to some procedural technicalities.

It's an effort to meet the General Assembly's requirement that fares pay half the cost of the train service. In the 1984 fiscal year, they did, according to Joe Nessel, passenger services specialist for the state railroad agency, but in the current 1985 fiscal year they've fallen to a projected 48 percent. The increase would bring the figure back to half-and-half.

The state subsidizes 24 daily trains on three routes: two routes on the Baltimore & Ohio (Chessie System) railroad, from Baltimore's Camden Station and from Brunswick into Washington, and one route on the Amtrak rails, from Baltimore's Pennsylvania Station into Washington. (The B&O and Amtrak Baltimore routes serve different intermediate communities.)

The main villains forcing a fare increase, Nessel said, are competition from Metrorail's new Red Line and higher equipment-leasing costs on the Amtrak route.

The bottom line of this story is the bottom line of commuter costs: monthly tickets from Brunswick to Washington would rise from $110 to $119; from Gaithersburg (on the B&O line) and Odenton (on the Amtrak line) from $77 to $83; from Laurel to Washington from $71 to $76, and from Baltimore, from $93 to $100 on the B&O line and from $99 to $107 on the Amtrak line, whose Baltimore station is three miles more distant.