A controversial study drafted for the Virginia highway department has recommended tightening car pool rules on I-66 inside the Capital Beltway in an attempt to ease traffic congestion.

The report, drafted by JHK & Associates, a consulting firm, and expected to be endorsed by the Virginia Department of Highways and Transportation, called for expanding the morning and afternoon rush-hour periods when car pool restrictions are in effect.

The study also concluded that current regulations, which require at least three persons in each car at rush hours, cannot become permanent.

As traffic increases, the report said, the limit should be revised to the initial requirement of four-member car pools.

Rep. Frank R. Wolf (R-Va.), who won congressional approval in 1983 of a measure to relax car pool rules on I-66, said yesterday he is "strongly opposed" to the new plan. "I just don't think that's going to happen," he said.

Wolf contended that rules mandated by Congress had "made a tremendous difference" for commuters and had "taken traffic off residential streets."

Any tightening of car pool regulations would require federal approval, and Wolf said he would seek to block such moves.

In another development, Virginia highway officials announced that a long-delayed traffic control system on I-66 and Shirley Highway (I-395) is to go into operation in about three weeks.

The $22.9 million system, which includes signal lights at ramps, has stirred widespread controversy.

Highway officials have argued that the computerized system will improve the flow of traffic on the two highways, but other local officials have charged that it may result in delays at ramps and backups in surrounding neighborhoods.

The system has been delayed for two years because of construction and other problems.

The I-66 report, outlined at a meeting of Virginia, District and federal transportation officials, said changes in car pool rules are warranted because of increased congestion, chiefly just before and after the rush hour restrictions.

"Between 6:00-7:00 a.m., I-66 is the most congested facility in the corridor," a summary of the draft report said.

"The congestion on I-66 has caused van pools to shift to I-395, has degraded access to Dulles airport after 6:00 p.m., and especially has caused car pools to shift travel hours out of the desirable, derestricted time slots."

Under the Wolf-backed legislation, car pool requirements are now in effect from 7 to 9 a.m. for eastbound traffic and from 4 to 6 p.m. for westbound commuters. The report urged expanding the hours to 6:30 a.m. to 9 a.m. and 4 p.m. to 6:30 p.m.

Under Wolf's measure, the rules were relaxed to allow cars with three individuals instead of four. The study found that this shift initially had "substantially improved the effectiveness of I-66 in moving people," but it warned that a long-term increase in congestion is likely.

Between 1990 and 1995, the consultants predicted, traffic growth will result in "a significant enough degradation of speed to serve as a disincentive to car pool formation and use of I-66."

At that point, the report said, four-member car pools should be required.

While opposing most of the consultants' proposals, Wolf said he would consider one possible shift. On weekday mornings, he said, car pools might be required from 6:30 to 8:30 a.m. instead of from 7 to 9 a.m.

In other developments, officials announced plans for a study of moves to reduce congestion on I-66 west of the Beltway, including possible restrictions on car pools.

They also reported a sharp rise in traffic on Shirley Highway's express lanes because of the recent easing of car pool rules.