District of Columbia officials have decided to relax auto emissions inspection standards substantially when a new, mandatory program takes effect Jan. 12, because too many cars were flunking the test under a trial program this year, according to the city Department of Transportation.

Starting Jan. 12, automobiles registered in Washington will have to undergo emissions tests as part of annual safety inspections, and owners will be required to repair cars that fail the test. Under the current voluntary emissions testing program, which went into effect last January, all cars are tested but owners are not required to repair those that do not pass.

About 15 to 20 percent of cars inspected are expected to flunk the new test and will have to be repaired and reinspected within 20 days, said Bob Kozac, inspection maintenance program manager.

Between 30 and 40 percent of the cars tested this year failed, Kozac said. He said the standards used in the voluntary program were more stringent than necessary to meet federal clean-air requirements.

Under the mandatory program there will be five categories of emissions standards, depending on the model of the car. They range from ceilings of 2,000 parts of hydrocarbon per million and 12 1/2 percent carbon monoxide for pre-1968 models to 300 parts of hydrocarbon and 1 1/2 percent carbon monoxide for 1980 models or newer.

Meanwhile, the typical end-of-the-month jam-ups at the city's two auto inspection stations were aggravated this week by the holidays, which meant fewer inspection days and less staff to test cars. Because of New Year's Eve, yesterday was the last day of the year on which inspections could be done.

The line at the station at Half and M streets SW curled around the block, and the wait was over an hour, according to a number of drivers in the line.

About half the people in the line said they were late getting their inspections, with the reasons ranging from the holidays to being out of the country for months to having the car in the shop.