The Fairfax County Board of Supervisors, alarmed at the increasing number of truck accidents on the Capital Beltway, yesterday renewed its call for a ban of large trucks from the left lane of the congested highway.

"The increase in truck accidents is becoming an epidemic," said Board Chairman John F. Herrity.

The board voted 7 to 0 to urge the Virginia Highway and Transportation Commission to ban the large vehicles from the passing lane of the Virginia segment of the Beltway from Cabin John Bridge to the Woodrow Wilson Bridge.

Maryland will prohibit all heavy trucks in the left lane of the Beltway between Woodrow Wilson Bridge and Georgia Avenue (Rte. 97) beginning Dec. 1.

A similar proposal in Virginia has been thwarted by intensive lobbying from trucking associations and other safety considerations. The state highway commission is scheduled to consider the proposal again Sept. 20.

The most recent major Beltway incident in Virginia occurred early Friday morning when a tractor-trailer rig loaded with mail slammed into the rear of an 18-wheeler carrying large concrete culverts. One driver was seriously injured when his truck exploded in flames and rush-hour traffic was tied up for almost four hours.

"I drive the Beltway every day," said Mason District Supervisor Thomas M. Davis who travels the highway from his home in central Fairfax to his office in Reston. "It's an exception when there's not a truck accident."

In the first six months of 1984 alone, there were 198 Beltway accidents involving tractor-trailers, according to the American Automobile Association. The Fairfax board first asked state highway officials to ban tractor-trailers from the left lane of the Beltway almost a year ago.

Similar bans have been tested in other areas and "there has been no reduction in accidents," said Shiva Pant, director of transportation for Fairfax County.

"You may be creating a whole convoy of trucks in the lane where cars are entering and exiting the highway," said Pant in an interview.

"It's not just a simple matter."

The Fairfax board also voted unanimously to ask the state legislature to give county police authority to ticket overloaded or unsafe trucks, which present other safety hazards on the county's roads.

A recent State Police report stated that 60 percent of the dump trucks stopped in a recent Northern Virginia survey -- most of them carrying sand, gravel or cement to construction or dumping sites -- were operating with unsafe brakes or tires, according to Supervisor Audrey Moore who represents the Annandale District.

Under present law, only State Police are authorized to stop and ticket heavy trucks. Moore said only 30 troopers statewide are assigned to that detail. Northern Virginia has only two scales for weighing large trucks, another hurdle in enforcing the weight limitations because of a state law that prohibits trucks from being diverted more than 10 miles for weighing.

One is on I-95 near Dumfries and the other west of Fairfax City on I-66.

In other action, county officials reported that the troubled Media General Cable television service has met construction requirements for cable access, but is falling behind in providing service.

"Cable construction activity is far outstripping Media General Cable's capability to market and install its subscribers today," a report said. "This accounts for the minimal 11,608 subscribers to date."

That represents only about one-fifth of the 53,418 homes that now have access to cable wiring, the report said.

"They may have the capability to install the cable," said Lee District Supervisor Joseph Alexander. "But they're not able to get anybody to knock on the door to offer the service for two to three months."

The Richmond-based cable company, which met its construction requirements with a four-month deadline extension from the board, said it is now adding more sales representatives to its staff because of the backlog.

The company reported that about 55 percent of the potential subscribers contacted have purchased cable service.

The board returned from its month-long summer recess yesterday without a representative for the Mount Vernon District.

Former supervisor Sandra L. Duckworth gave up her seat to join her family in Hawaii, where her husband has been appointed director of a prestigious museum. Also absent from the meeting yesterday was Centreville Supervisor Martha V. Pennino who is recovering from surgery.