Ever since 1974, when the federal government enacted a national 55 miles-per-hour speed limit, truckers and other driving interests have argued that higher speeds would save time -- some even said gasoline as well -- and that time is money and . . .

As vacationers head for their cars -- 95 million Americans, according to the American Automobile Association, are expected to travel at least 100 miles from home between Memorial Day and Labor Day -- the National Safety Council has issued a couple of critical reminders:

The chances of a person being killed in a car collision doubles with each 10 mph of speed over 55 mph.

It is estimated that as many as 80,000 lives may have been saved by imposition of the 55 mph speed limit. The council notes that the "mileage death rate on the nation's highways for 1985 was 2.58 per 100 million miles traveled, compared to the 1973 before the limit mileage death rate of 4.24."

The council, a nonprofit, nongovernment public service group, is asking Americans to match their driving habits to their stated attitude: Although regular polls taken by Gallup and other groups indicate Americans want to keep the 55 mph speed limit, law-enforcement organizations across the country are reporting a driving public moving at only slightly under the speed of sound.

The use of radar detectors (illegal in the District, Virginia and Connecticut) is soaring, the CB radio airwaves are filled with warnings of "Smokey Bears" (state police) and "County Mounties" (local police) with "picture-takers" (radar), and people doing 55 on the open road often feel as though they're crawling, compared with the rest of the traffic.

With a static number of enforcement units and an accelerating number of speeders, the majority are getting away with their heavy-footed driving.

Even though the number of drivers complying with the 55 mph limit since the law's adoption has dropped, a council spokesman says that the number of speeders remains far below the number of speeders in 1974 and before.

"The end result," says spokesman Al Lauersdorf, "is more lives saved. People who oppose the limit claim it is not a proven lifesaver, but the facts prove otherwise."

The facts also indicate speeding does not mean substantial savings of time on the road. In a test run by the Minnesota Safety Council, two drivers drove the same 1,000-mile course: "The fast driver passed 2,000 cars, braked 1,339 times and covered the distance in 20 hours, 12 minutes. The slow driver flowed with traffic, passed only 13 cars and braked 652 times. It took him 20 hours, 43 minutes."

The faster driver saved 31 minutes but used 10 gallons more gasoline. SADD

"Drunk driving," declares Robert Anastas, "is the No. 1 killer of young people 16 to 20." Anastas, the Massachusetts high school teacher and coach who founded Students Against Drunk Driving (SADD) after two of his pupils were killed in traffic accidents, says 8,000 young people die each year because of drunk driving.

Anastas is spreading his message -- that things don't have to be this way -- in The Contract for Life (Pocket Books, 157 pp., $4.95), a book about how and why SADD came to be and how it works.

The program has been successful: Since SADD was established, teen drinking has dropped by 10 percent, and the death rate attributable to drunk driving by teen-agers has dropped by 33 percent. Still, Anastas says, "We cannot rest until no young person is robbed of his or her future by this needless tragedy."