Virginia State Police, who have been fielding as many as 10 complaints a day about reckless truck drivers on the Capital Beltway, will triple the number of troopers patrolling the Beltway starting Monday.

Twelve troopers, instead of the usual four, will patrol Virginia's 23-mile stretch of Beltway in marked and unmarked cars between 7 a.m. and 11 p.m. in a one-month experiment designed to reduce tailgating, speeding and other causes of accidents, according to Maj. Charles M. Robinson of the Virginia State Police. The results of the experiment will be evaluated in November.

Robinson said the decision to increase the number of troopers is part of an ongoing state police program, called the "selective enforcement program," to allow police to zero in on certain troubled roads.

During the first nine months of this year, the Beltway was the scene of 488 accidents. Nearly 116, or 25 percent, of those involved tractor-trailers, state police say.

"It's usually either tailgating or lane-changing," said Lt. Herbert D. Northern, acting commander of the Northern Virginia Division of State Police, adding that the most dangerous part is the heavily-traveled stretch between the Woodrow Wilson Memorial Bridge and the Rte. 395 interchange.

The problem is not just with trucks, he said. During the first eight months of this year, Beltway troopers cited or arrested l8,448 motorists for various offenses. Of those, 4,394 were truck or bus drivers.

"We've been getting complaints for some time," said Northern, "about the trucks, about all the motorists."

Troopers stationed at the Braddock Road barracks will work overtime and on days off to comply with the new schedule. In addition, four troopers will be borrowed from the Arlington office, Northern said.

He said he was not certain how much overtime will be required, or how much the experiment will cost.

"I think it's an excellent idea," said Tom Crosby, spokesman for the American Automobile Association in the Washington area.

"My understanding is that the state police are working their butts off," he said. "They're a good, hard-working state police department, and very professional, but when they're undermanned, there's not a hell of a lot they can do."

Crosby said congestion, plus the Beltway's blend of big-rig trucks, tourists, shoppers and commuters, make it particularly dangerous.

David Gehr, Northern Virginia district engineer with the state highway department, also applauded the increased patrols.

"Human beings being what they are, they'll tend to obey all traffic laws when they know somebody is watching them," he said.

The state highway commission last month rejected by a 5-to-4 vote a motion that trucks be banned from the Beltway's left lane, on grounds that the action would not cut accidents.

Commissioners are scheduled to reconsider the issue on Oct. 24, according to Joe Presbrey, a highway department spokesman.

In Maryland, officials said there has been no change in Beltway enforcement, or in the number of troopers on patrol.

However, starting Dec. 1, trucks using the Maryland portion of the Beltway will be prohibited from using the far left lane.

The ban is part of a one-year experiment to determine what effect trucks have on the number and seriousness of Beltway accidents, said Michael Snyder, district engineer for the state highway administration.