D.C. police arrested 39 people on drunk-driving charges early yesterday at a Canal Road checkpoint in Georgetown where hundreds of motorists were stopped, questioned and examined for signs of intoxication.

A sign that read "Stop Ahead. Drunk Driving Checkpoint" surprised drivers at midnight just east of the Canal Road entrance to Georgetown University. As they inched along a smoky corridor of burning road flares, each car was stopped, and officers pointed a device at the drivers that looks like a flashlight but picks up traces of alcohol on the breath.

"Sorry to impose on you, sir," one officer told the nervous driver of a blue Volvo, "but would you pull your car over to the side of the road? We're looking for drunk drivers, and you've been drinking." The motorist then passed a series of coordination tests that showed he was not impaired and was sent on his way, looking greatly relieved.

Yesterday's drunk-driving checkpoint was the second conducted by D.C. police. Authorities arrested 43 drivers in June at a roadblock on New York Avenue in Northeast Washington. Police officials call the roadblocks "a last-ditch effort" to combat the burgeoning problem of drunk driving.

"We've had 47 traffic fatalities so far this year, and 22 have been alcohol related. At this time last year we had only seven alcohol-related traffic fatalities," said Robert M. Goldstein, director of the police department's alcohol counter measures and police traffic services. "DWI driving while intoxicated arrests are up 53 percent this year, and we're only scratching the surface."

Of yesterday's 39 arrests, 28 were male and 11 were female, said Goldstein. Eleven were under 21 years old, a figure that contrasted sharply to the New York Avenue arrests, in which only one was under 21. Eighteen had Maryland license plates, 12 had District tags, and seven had Virginia license plates.

Court dates for those arrested yesterday have been set for September. Penalties for a first offense can range up to $300 in fines and/or up to 90 days in jail and rise sharply for multiple offenders. Some officers at the checkpoint privately grumbled that offenders rarely receive the maximum sentences.

At the checkpoints, said police Capt. James G. Brunzos, nine officers stopped cars to check each driver for slurred speech or glazed eyes and to check the cars for alcoholic beverages. Motorists suspected of being too drunk to drive were pulled over to perform traditional sobriety tests like walking a straight line and counting backwards, said Brunzos. Those who performed poorly were then given a breathalizer test to determine the alcohol content of their blood.

A blood alcochol content of .05, which could be found, for example in a 140-pound to 160-pound person who has just quaffed two 12-ounce beers, means a person is considered legally under the influence of liquor and should not drive, according to police. With a blood alcohol content of .10, a driver is legally considered intoxicated.

Arrests were processed in three drunk-driving wagons with their own small lockups. Goldstein said U.S. Park Police, Virginia state police and Arlington County police had been notified of the roadblock in case any motorists tried to elude it by driving over Key Bridge to the George Washington Parkway. Neither jurisdiction reported any arrests related to the roadblock.

Even some who were arrested or delayed yesterday saw some merit in the roadblocks.

"I think it's good, but it's unfair to vegetarians," said a MacArthur Boulevard resident among those arrested. "Meat absorbs alcohol better, you know. They didn't buy that."

Yesterday's roadblock caused no massive traffic problems, in part because police would occasionally let cars roll through when they became too bogged down in processing and, perhaps, because news of the roadblock had been spread in advance.

It was the light traffic that led to mixed feelings about the roadblock on the parts of restaurateurs and bar owners along the M Street corridor. Some complained of smaller-than-normal crowds last night and speculated that the news of the roadblock might have prompted some customers to spend Friday night outside Georgetown.

"As a citizen, I think it's not a bad idea, . . . from a business standpoint, I'm really not crazy about it," said Prem Devedas, manager of the Lion's Gate Tavern. Douglas Karroll, manager of Nathan's, echoed similar apprehensions and said he thought an increased police patrol presence would be a better solution.

Kamal Jahanbein, owner of The Saloon, doesn't agree with his colleagues. He said he is so upset about drunkenness in Georgetown that he is moving his business. "I am for it the roadblocks ," said Jahanbein. "But I'd rather see them arrested before they get into their cars. People are already drunk before they come in here."

Goldstein said that returned questionnaires from motorists stopped at New York Avenue indicated that 88 percent approved of the concept.

One young man, clad in jeans and sneakers and wobbling as he tried with limited success to walk a straight line at the checkpoint yesterday, certainly didn't like the idea. "My mom," he said ruefully, "warned me about these roadblocks."