Metrobus routes throughout Northern Virginia will be revised with the opening of I-66, shortening rides for some commuters and increasing fares for others, under proposals that will be argued in a public hearing Tuesday.

In June, the stretch of I-66 between the Beltway and Glebe Road will open to Metrobuses--but no other vehicles--providing express bus service from outlying communities to the Ballston Metro Station, according to David Erion, executive director of the Northern Virginia Transportation Commission.

The highway is scheduled to open for automobile traffic in October, after the section from Ballston to the Potomac River is completed, Erion said.

The Metro Board has proposed revising bus service on 11 routes, eliminating service on four routes and rerouting buses on another line.

The proposed changes, drawn up by the board's planning staff, would cut the time of some rides by up to 24 minutes but would increase the cost of others by 75 cents for a round trip.

The Metro Board will conduct its first public hearing on the proposals at 7:30 p.m. Tuesday in the board room of the Massey Building, 4100 Chain Bridge Road, Fairfax. A second public forum will be at 7:30 p.m. Jan. 20 at George Mason Junior/Senior High School, 7124 Leesburg Pike, Falls Church.

After the public hearings, the board is expected to spend about 1 1/2 months considering the public comments and recommendations from local government agencies before making the bus routes final, Erion said.

"I would expect the most opposition to come from folks who will have to pay more," said Erion. "For most people, the new routes will mean an improvement in service."

Costs would go up by 75 cents round trip for riders on some routes to the Pentagon. Buses now take passengers on Vienna, Fairfax Circle and Brookfield lines directly to the Pentagon. Under the new proposals, however, those riders would have to transfer from a bus to Metrorail at the Ballston station. That switch would cost them an additional 75 cents for each daily round trip and boost their fare to $3.45.

Some passengers would enjoy a reduction in fares under the proposals. The Reston-Farragut Square round-trip bus and rail fare would drop 45 cents to $3.45.

Erion said the emphasis of the schedule changes is to reduce travel time for passengers taking buses to the Ballston Metro station. The opening of I-66 to the buses will provide an express route to the station, shaving travel time on all but one route. The Vienna-Federal Triangle ride would be reduced from 65 minutes to 41 minutes under one proposed change.

Proposed changes would eliminate some bus lines in Fairfax City and Falls Church, according to Erion. He said Fairfax City is expected to cover those losses by adding service to its own privately contracted bus line.

Metro board officials estimate that the route changes in Northern Virginia will reduce local subsidy requirements by about $135,000 annually, as consolidating routes will reduce miles traveled.