Two major train lines that carry thousands of commuters between Maryland and the District are expected to be shut down today by railroad workers refusing to cross a picket line thrown up yesterday by electrical workers, railroad officials said.

An estimated 7,600 commuters who ride the Maryland Rail Commuter Service trains into Union Station will have to hunt for alternative transportation at a time when a strike by Greyhound bus employees already has cut into available public transportation in the area.

Robert Shreeve, a spokesman for the Maryland State Railroad Administration, said commuters who ride the Brunswick and Camden lines will be affected. "We will try to put additional equipment on {other} lines, but it will be crowded," Shreeve said.

A union official estimated that 300 workers in the District, Maryland, Pennsylvania, West Virginia and Ohio would honor the picket line.

Eighty railroad workers from the International Brotherhood of Electrical Workers went on strike yesterday at CSX's Cumberland, Md., train yard to protest the layoff of 45 workers from the repair shop there. They also were upset over the company's decision to give crane operator positions to workers in other crafts.

"We have been very encouraged by the support we've been shown by other employee organizations," George Laitila, a regional representative for the electrical union, told the Associated Press.

The Brunswick line carries about 5,100 commuters. It runs between Martinsburg, W.Va., and Union Station, and goes through Frederick and Montgomery counties, with stops including Germantown, Gaithersburg, Rockville and Silver Spring.

The Camden line takes 2,500 commuters between Baltimore's Camden Station and Union Station, with stops in Howard, Anne Arundel and Prince George's counties.

Shreeve said Camden Line commuters can use their tickets on the Amtrak's Penn line, which has 36 trains a day beginning at 5:30 a.m., and that Amtrak is trying to add another two trains to the route.

The Brunswick line riders, however, "are just going to have to find alternative transportation," he said.

A CSX spokesman, Lindsay Leckie, said the company plans to seek an injunction in federal court today to stop the strike. "We don't feel it's a proper work stoppage," he said, adding that the layoffs were driven by the retirement of 200 locomotives. "We're always adjusting our operations and practices," he said.

Leckie said that supervisory personnel are running the company's freight trains and that freight service will not be affected. CSX operates in 20 states and employs 37,500 people, he said.

For information on available train lines, CSX asks commuters to call 1-800-325-RAIL.