Buses skid and flip over. Tractor-trailers jackknife and overturn. Cars career across median strips and crash head on with on-coming traffic. Trucks catch fire. One fender bender leads to a chain reaction in bumper to bumper traffic.

Such is the steady diet of those who travel the Capital Beltway to and from work each day and yesterday seemed especially night-marish.

There were 11 accidents in all, three of which were major, police said.

First, two tractor-trailers - one carrying automobiles - collided on the Woodrow Wilson bridge at 3 a.m., pouring some 30 gallons of diesel fuel onto the road, police reported. Police said the road was a virtual skating rink as highway officials worked through the early morning hours to wash and sand over the road so it would be safe for the morning rush hours.

Then about 5 a.m. on the Virginia Beltway, a 55-foot-long tractor-trailer collided with a 10-ton milk truck near the southbound exit for Braddock Road, causing a traffic backup of at least a mile.

Finally about an hour later, the rear wheel of a flathed trailer caught fire on an eastbound loop of the Beltway at the Georgia Avenue exit. One lane of traffice had to be closed, causing delays to morning motorists, Montgomery County police reported.

Traffic delays on the Beltway whether they're caused by accidents Metro construction, or the sheer volume of cars, are becoming more frequent, officials say. Since 1964, the number of vehicles that pass through the Georgia Avenue section of the Beltway in Maryland has doubled to about 168,000 each day, according to Slade Caltrider, district engineer for the Maryland Highway Administration.

"It gives me heartburn," said one commuter, Pat Maier, 25, who spends a half-hour on the Beltway each morning driving from Georgia Avenue to the Rockville exit. "Everybody drives fast, so you have to be an aggressive driver.

"By the time I arrive at my office, I feel as though I've already done an hour's work just because of the driving," said Maier, a planner for Montgomery County.

Police say, however, that the Beltway drivers are their own worst enemies. Most of the accidents occur when drivers go over the speed limit, which varies from 50 to 55 miles an hours, follow the car in front of them so closely they cannot stop quickly enough to avoid a collision, or when they make rapid changes from one lane to another.

But the raod design does not help either, police said.

In Montgomery County, police have identified the major trouble spot as the stretch between the Beltway's Georgia Avenue and Wisconsin Avenue exits. This section of the Beltway has been nicknamed the "Rock Creek Rollercoaster" because of the way it twists and turns as it crosses Rock Creek Park.

"Generally, one-car accidents occur at the first hand curve where the Beltway passes the Mormon Temple," said Officer Rick Nelson, Montgomery police spokesman.

Between the heavily traveled River Road and Wisconsin Avenue exists the eastbound lanes narrow from four lanes to two, causing a number of accidents as bewildered drivers suddenly merge, he said. A similar situation exists in the westbound lanes where the road narrows sbruptly from three to two lanes in a matter of 200 feet, Nelson said.

But help - in the form of a mixed blessing - is on the way for Maryland commuters, according to Caltrider. He said the highway administration is planning to add an extra lane in each direction, lenthen access ramps, and install concrete dividers where not exist only grassy grassy median strips. But the construction is still three years away, he said. And whenever the construction does begin, traffic declays - and accidents - are sure to follow.

Northern Virginia State Police report that accidents have been cut by about a third since the widening of the Beltway there from four and six lanes to eight. The widening project along the 22 miles of the Virginia segment of the Beltway took 3 1/2 years, and greatly relieved problems of congested traffic there.

At the same, time, however, an estimated 3,600 accidents occurred during the construction to many of which have been attributed to construction hazards, according to police.

Last year on the Maryland section of the Beltway, meanwhile, 264 persons were injured in accidents, according to Maryland State Police.

"When Beltway accidents happen, they are sensational, said, Caltrider, "but the fact remains that the road has a relatively low accident rate" for highways in Maryland.