Arlington County Board members spent much of Saturday plowing through the county's master transportation plan, a general design for the county's 450 miles of roads that has not been updated since 1975.

Board members did not complete the complicated process Saturday, but they did make decisions on major portions of the plan.

For instance, they reaffirmed future consideration of a longstanding proposal to make Arlington Boulevard (Rte. 50) a limited access highway in order to encourage smooth traffic flow and discourage cars from shortcutting through residential neighborhoods.

But before embarking on such a plan, which has been attacked by many residents on each side of the highway as inconvenient, board members agreed to try more moderate means to facilitate traffic flow and keep it off residential streets, such as prohibiting turns into side streets during rush hours, when the problem is worst.

Board members also reaffirmed plans that could lead to the widening of major thoroughfares in the county, including Glebe Road, Wilson Boulevard and Lee Highway.

Plans include the widening from four to six lanes of the 1 1/2-mile stretch of Glebe Road between Arlington Boulevard and I-66, the eight-block section of Lee Highway between North Kenmore and North Quincy streets, and the one-mile stretch of Wilson Boulevard between Washington Boulevard and Glebe Road.

Tied into the widening of Wilson Boulevard was the board's decision to keep as an option the construction of a vehicular underpass on Washington Boulevard beneath Wilson Boulevard.

Board members took a special look at what the intersection of Wilson and Washington boulevards might look like after Wilson and Clarendon boulevards are widened to six lanes. They expressed concern about the safety of motorists and pedestrians traveling through the massive intersection and decided not to strike from the transportation plan the possibility of building the underpass.

"All the widening will create a huge intersection," said Mark Kellogg, the county's public works planning supervisor.

"It's not going to be very attractive, and it's going to be difficult for pedestrians to use" without an underpass, he said.

In addition to approving in concept plans to widen some roads, board members agreed to narrow from four to lanes two an eight-block section of Pershing Drive between North Garfield Street and North Oxford Street. Residents living near the section have lobbied for the narrowing to reduce traffic and increase safety.

The board also:

Reaffirmed its desire to add a third westbound lane to a half-mile stretch of the George Washington Parkway between Rosslyn and Spout Run Parkway.

Directed the county staff to work with residents who want the county to narrow the 1 1/4-mile stretch of Lorcom Lane between Spout Run Parkway and Old Dominion Drive.

Approved in concept a plan to construct a three-block, four-lane section of North Quincy Street that would connect Wilson Boulevard and Glebe Road, pending relocation of the Metrobus garage.