The Metropolitan Washington Council of Governments agreed yesterday to hold a "high-powered" full-day conference in December or early January on ways to improve traffic safety on the Capital Beltway and restrict trucks carrying hazardous cargo.

The decision to hold the conference comes less than a week after a tanker truck carrying 1,600 gallons of propane fuel turned over on the Beltway, forcing the closure of the highway for about three miles and the evacuation of hundreds of area residents from their homes. Last month, a truck carrying corrosive chemicals crashed on the Beltway in Fairfax County forcing the evacuation of 630 people from nearby homes.

John J. Bosley, COG's general counsel, said 100 to 150 federal, state and local officials would be invited to the conference along with representatives from the American Trucking Association.

"The intention is not to be critical but to look at means of alleviating the problem," he said. The Board of Trade will cosponsor the conference.

Fairfax County Supervisor Nancy K. Falck said after the meeting that she was "very pleased" with COG's decision. "We are all very interested in working successfully towards increasing safety on the Beltway. We want to pull everybody together and come up with a good plan of action and make our Beltway safe."

On trucks bearing hazardous cargo, Falck said, "We need to have a good technical look at what is hazardous cargo and what protection and prevention can be taken against it."

In July, the COG board of directors passed a resolution that called for banning trucks from the left lane of the Beltway, increasing the presence of police and establishing a minimum speed limit.

The Beltway is a 67-mile circumferential highway in suburban Maryland and Virginia, about 12 miles outside the District. According to 1983 traffic statistics from Maryland and Virginia, about 125,000 vehicles a day used the Beltway in Maryland and about 115,000 vehicles a day in Virginia, including 23,000 trucks.

In the first six months of this year in Maryland, 859 accidents occurred on the Beltway, 196 involving trucks. For the same period in Virginia, 231 accidents occurred, 55 involving trucks. The statistics also state that if the current patterns continue, 2,318 accidents would occur on the Beltway this year, of which 535 will involve trucks.

In other action, COG approved a seven-point plan proposed by D.C. Mayor Marion Barry to assure that D.C. residents can learn of suburban jobs. Earlier this year, it was reported that suburban employers were having difficulty finding workers. The city's current unemployment rate is 8.9 percent, nearly double the rate for the metropolitan area.