An article yesterday incorrectly reported statistics on traffic fatalities in Montgomery County. The number declined from 21 to 19 in the first six months of this year from the same period in 1982.

Despite a crackdown on drunken driving, the District of Columbia has recorded a steep increase in traffic fatalities this year, reversing a steady decline since the mid-1970s and causing alarm among safety officials.

Forty-two persons have died in traffic accidents in the city this year, according to police statistics. The number of fatalities already exceeds the total killed in all of 1982, when the District reported 36 traffic deaths. This year's total also is more than twice the 18 deaths reported as of July 18 of last year.

Of the 42 deaths this year, 21 occurred in accidents involving consumption of alcoholic beverages, officials said. In comparison, six alcohol-related fatalities were reported during the same portion of last year and a total of 14 in the entire year.

"We're just being overwhelmed by the sheer numbers," said Robert M. Goldstein, director of the D.C. police department's Alcohol Countermeasures and Police Traffic Services. "This is the first year in seven years that it's going up--and it's going up at such an alarming pace."

"It's scaring the daylights out of us," said William Corgill, safety coordinator for the D.C. Transportation Department. "It's just reversed the trend for no reason that we can put our finger on."

The abrupt turnabout in the District appears to mark a departure from trends elsewhere in the country. The National Safety Council has reported a 1 percent decrease in traffic deaths nationwide during the first three months of this year, after a 10 percent decline in 1982.

In Maryland and Virginia, downward trends also have continued, officials said. Maryland has recorded 300 traffic fatalities this year, compared with 322 during the same period last year. In Virginia, 427 deaths have been reported, eight fewer than during the same period of last year.

In the Washington area, Fairfax County reported 19 traffic fatalities as of June 30, a decrease from 24 during the first six months of last year. In Arlington County, four traffic deaths have occurred, compared with 10 reported during all of 1982.

Montgomery County, however, also has reported a sharp increase in traffic fatalities with 19 persons reported killed as of June 30. During the first six months of last year, county officials said, six deaths were recorded. Officials said only one of this year's fatalities was alcohol-related, while all six of last year's fatal accidents involved consumption of alcohol.

Barbara Carraro, an analyst for the National Safety Council, said it is difficult to pinpoint causes of short-term fluctuations in traffic fatality statistics, especially in areas such as the District where totals are relatively small.

The District's stepped-up campaign against intoxicated motorists has resulted in 2,770 drunk-driving arrests during the first half of this year, officials said--a 53.8 percent increase over the first six months of 1982. The city's drunk-driving laws were tightened last year, and police recently set up a checkpoint where they arrested 43 allegedly inebriated drivers.

Because of this effort, Goldstein said he found it "more confounding" to observe the recent rise in traffic fatalities, many of them linked with alcohol use. He noted, however, that no alcohol-related death has been reported since the first police checkpoint was established on June 25, and he promised more checkpoints.

In the District, the number of traffic deaths first declined in the early 1970s, dropping from 121 fatalities in 1970 to 73 in 1972. Then the totals began decreasing steadily again after 1975, when the police started the campaign against drunken driving. With the exception of a slight rise in 1981, total fatalities declined every year until last year, when the city had the lowest number of traffic deaths ever recorded.