Montgomery County planning officials are expected to vote today on whether to study two routes for a light-rail line between Silver Spring and Langley Park, part of a proposal to improve east-west transit service in the Maryland suburbs.

Montgomery, Prince George's County and state officials have long debated the merits of a 14-mile Purple Line, or Bi-County Transitway, between Silver Spring and New Carrollton. Most of the focus has been on the proposed western segment between Bethesda and Silver Spring. Today, the Montgomery County Planning Board will consider routes through the eastern county, between Silver Spring and the Prince George's border.

"This is a critical link in the whole system," said Margaret K. Rifkin, an urban planner for the board. "Whichever end you start at, this is in the middle. If we're going to achieve that vision of this excellent east-west link, this is a piece that has to be addressed."

Like the Bethesda-Silver Spring segment, Rifkin said, the eastern Montgomery link poses a challenge to planners because it would run through densely populated areas. However, it would also serve the Long Branch and Takoma-Langley Crossroads communities, which have high bus ridership and need improved transit service, Rifkin said.

Planning staff members outlined two routes, both starting in downtown Silver Spring. One would run primarily along Wayne Avenue, and the other would essentially parallel Sligo Avenue.

Both would connect to Piney Branch Road near Flower Avenue, run along Piney Branch and turn east onto University Boulevard to Langley Park. There would be stations at 16th Street/Woodside, Silver Spring, Flower Avenue and the Takoma-Langley Crossroads area. Stations could be added at Fenton Street and Sligo Creek or Dale Drive, depending on the route, according to the staff report to the Planning Board.

Both routes assume that the Silver Spring Station would connect to a light-rail line running to Bethesda, along the Georgetown Branch. That route, which would bisect the Columbia Country Club golf course and run beside a popular walking and biking trail, has generated intense debate.

The Planning Board is scheduled to vote today on a staff recommendation to further study both eastern routes. The board's decision will go to the County Council, which will then make a recommendation to the Maryland Transit Administration.

The state is studying transit alternatives between Bethesda and New Carrollton, including light rail and bus rapid transit. A draft environmental study is to be completed by spring. Public hearings are scheduled for spring 2006 on the alternative that is chosen.

The cost is estimated at $1.7 billion, depending on the route, the tunneling required and whether light rail or bus rapid transit is chosen, said Jack Cahalan, spokesman for the Maryland Department of Transportation. Construction would begin in 2009 at the earliest, Cahalan said.

Ben Ross of Bethesda, president of the Action Committee for Transit, which supports a Purple Line, said he hopes the county will keep pushing the state to move on the transit link, which he worries is being delayed by the state study. He said neighborhood support for Montgomery's eastern link is strong, even though the rail line would run through developed areas.

"There are people in these neighborhoods," Ross said, "but people really want this transportation."