The Virginia Highway and Transportation Board, in a controversial move, voted yesterday to expand the hours during which car pool restrictions are imposed on Rte. I-66 inside the Capital Beltway in an attempt to reduce traffic congestion.

Starting Aug. 4, the highway's eastbound lanes will be limited to car pools with at least three persons from 6:30 to 9 a.m. Under the ruling, the three-person car pool requirement will be imposed on westbound traffic from 4 to 6:30 p.m. The restrictions now take effect at 7 a.m. eastbound and end at 6 p.m. westbound.

The board's move was immediately criticized by Rep. Frank R. Wolf (R-Va.), who won congressional approval of a 1983 measure that relaxed the car pool rules. A spokesman for Wolf said that the board had acted without an adequate study of the issue and described Wolf as "extremely disappointed."

The ruling was among several state and congressional actions yesterday to deal with mounting congestion in the Washington area. Other moves included:The House Appropriations Committee approved a plan, sponsored by Wolf, to provide $1.5 million in federal funds to build an additional inbound lane on the Theodore Roosevelt Bridge. Pointing to a recent federal study, Wolf contended that the proposed lane would benefit Northern Virginia commuters.

Plans to widen the Potomac River span, which is owned by the District, previously have set off objections from D.C. officials, who have cited concern over increased congestion on city streets. A D.C. Department of Public Works spokesman said city officials have not reviewed Wolf's measure. Congressional officials disclosed that the House Public Works and Transportation Committee had endorsed an amendment to make permanent an experimental plan that relaxed car pool restrictions on Shirley Highway. The committee acted last month, but the move was not announced at the time.

Under the experiment, which began in April 1985, the hours during which four-person car pools are required on Shirley Highway's express lanes were cut back. The restrictions now are in effect from 6 to 9 a.m. inbound and 3:30 to 6 p.m. outbound. A study, required as part of the experiment, has not been completed.

The amendment to retain the revised rules was sponsored by Rep. Robert A. Young (D-Mo.), a Burke resident, at the urging of Rep. Stan Parris (R-Va.). An aide to Parris, who had pressed for the earlier measure to ease the rules, said the amendment was adopted partly because of concern over delays in the study. The Virginia highway board allotted nearly $9 million for road improvements in Northern Virginia, including a plan to widen heavily congested Sully Road (Rte. 28) between I-66 and Rte. 7 and to improve an interchange between Rte. 28 and the Dulles Toll Road.

A spokeswoman for the board said the measures were among $63.5 million in stepped-up spending for highway expansion throughout the state financed by a recent increase in gasoline tax revenues. The General Assembly mandated the road work and it has been endorsed by Gov. Gerald L. Baliles.

The expanded hours for car pool restrictions on I-66 had been recommended last year in a consultant's study and endorsed by the Virginia highway department, the Metro transit system and the Transportation Planning Board, an affiliate of the Metropolitan Washington Council of Governments.

The consulting firm, JHK & Associates, said the expanded hours were warranted partly because of increased congestion shortly before and after rush-hour periods.

Nonetheless, the study endorsed another measure incorporated in Wolf's legislation -- a relaxation of the rules to permit car pools carrying three persons instead of four. State and federal officials have agreed to retain the three-person requirement, at least until congestion becomes more severe.

Wolf had argued that the state board should delay any change in the hours until it studied further the impact on traffic of last month's opening of a Metro subway extension along I-66 to Vienna. But state officials said recent data showed no significant decrease in congestion after the rail route opened.