Plans to widen the narrowest and most dangerous section of Washington's Beltway--the 3.5 miles between I-270 and Georgia Avenue--will be the subject of a public hearing at 7:30 tonight at Albert Einstein High School in Kensington.

The $43-million project would add two lanes, a wider road shoulder and more than a mile of sound barrier walls to the six-lane highway.

Even if these final design plans are approved, however, the state has no money for the Beltway project in its six-year construction program. The widening, which would take about two years, could start in 1987 if the state legislature approves an increase in highway taxes this year, according to assistant project manager Don Ayres.

The state rejected relocating this part of the Beltway in the early 1970s and has done extensive analyses of widening the existing curvy section. Built in the southern part of Rock Creek Regional Park, this segment of the Beltway does not meet current interstate highway standards because of its curves and has the worst traffic record for any part of the 20-year-old Beltway, according to state figures.

In the past 10 years, 10 people have been killed and 888 injured in almost 600 accidents in this section. Another 1,444 accidents resulting in vehicle damage but no injuries also were reported. The accident rate for this section has increased with traffic over the decade, and in 1979 was 194.5 accidents per 100 million miles traveled, compared to 109.5 for the rest of the Maryland portion of the Beltway, according to state figures.

If the roadway is widened, the accident rate is expected to drop about 25 percent, state highway officials predict, although they emphasize that traffic on the Beltway "will continue to increase regardless of the alternative selected."

If the roadway is not widened, the environmental assessment predicts, the six-lane section of the Beltway will become so jammed that traffic will spill over onto neighborhood streets in large numbers, perhaps as many as 17,000 additional cars a day.