The time was summer 1975 and the numbers weren't cheerful. Traffic deaths in Maryland at midyear were more than 15 percent above the midyear total of the previous year.

Col. Thomas S. Smith, the state police commander, paced his office, seeking inspiration. He glanced out his window. There, Smith spotted a clunky 1957 pickup truck that police had seized in a raid.

Thus was born Maryland's reputation as one of the nation's toughest - and easily the nation's cleverest - enforcer of the 55 mile-an-hour speed limit.

The pickup truck that Smith spotted was taken to the State Highway Administration, where it was loaded with hay and fitted with a concealed red flashing light. Then, with a policeman driving, The Haywagon headed for Interstate 95. It has been overtaking and ticketing some very startled speeders ever since.

As Maryland enters the summer driving season, and winds up its fourth year of 55 mile-an-hour limits on its superhighways, The Haywagon has become something of a legend. But it has some colorful cousins.

Perhaps the gaudiest (some would say sneakiest) is Mother Goose.

An 18-wheel semitrailer confiscated in a police drug raid, Mother Goose's mission is to pose as just another truck and to slip in among convoys that are exceeding the speed limit. After a few miles, and some radar readings, Mother radios ahead to waiting police, who arrest the entire pack of truckers.

The same approach is used with what state police formally call "other nonconventional police vehicles." Campers, battered Volkswagens, rusted-out Chevies - all are used in highway speed enforcement.

Police have received considerable criticism for their unusual methods. One Eastern Shore man has dubbed the state police chief "Col. Haywood Smith," and sends him harassing postcards.Two citizens who met The Haywagon the hard way unsuccessfully sued the police, charging entrapment.

But the results speak for themselves.

Maryland is one of only two states (Massachusetts is the other) to have reduced its highway death toll in each of the four years from 1974 to 1977. According to police projections, 1978 will follow suit.

According to U.S. Department of Transportation (DOT) figures for the first half of 1977, Maryland was 11th best among the 50 states in the percentage of its drivers (46.5) who were exceeding 55 miles an hour on super-highways. Connecticut and Wyoming (23 percent observed the limit) were the nation's worst states. Virginia (72 percent) was the nation's best.

Maryland also ranked 11th in the average highway speed of the "average car" (55.1 miles an hour - the national average was 56.4).

The state's mediam highway speed of exactly 53 miles an hour ranked it 13th. Its 1977 death rate of 2.23 per 100 million vehicle miles was third best in the nation.

The number of speeding tickets given by state police has risen dramatically since 55 became the speed limit. In 1974, 106,000 tickets were issued. The total has risen steadily every year since: 183,000 in 1975, 203,000 in 1976, 231,000 last year.

Meanwhile, fatalities fell from 822 in 1973 to 737 in 1974, 692 in 1975, 678 in 1976 and 674 last year. These figures came despite an average annual increase of 5 percent in total statewide vehicle miles.

One area in which Maryland is only average is in the severity of its speeding penalties.

Some states provide fines of as much as $1,000, and jail terms of as much as a year. But in Maryland, for exceeding the limit by less than 10 miles an hour, a speeder may be fined $30. Ten to 19 miles over the milit is $40, 20 to 29 miles over is $50. Thirty or more miles over the limit requires a court appearance.

State law does not provide jail terms for speeders, although they have "points" applied to their driving records.

In addition to its array of unmarked police vehicles, Maryland has an unusual program of speed enforcement that targets the stretches of road where most of the state's speeding and accident occur.

The program, called Operation Yellow Jacket and funded by a $179,000 DOT grant, has just finished its first year. It focuses on drunken drivers as well as speeders. The bulk of the federal funds pay for police overtime.

Much of the Yellow Jacket effort has been concentrated on the Baltimore suburbs, and on U.S. 29 and U.S. 1 northeast of Washington. Police use hand-held radar guns to clock speeders. More than 10,000 Yellow Jacket arrests were made in the program's first year.

The other major Maryland speeding program went into effect over the Memorial Day weekend. Called Operation CARE (for Combined Accident Reduction Effort), it is designed to crack down on speeders along Interstate 95, the major East Coast Maine-to-Florida route.

State police in the 15 states through which 1.95 runs are participating. The program will last through the summer, with particular emphasis on the Independence Day and Labor weekends.

Meanwhile, Maryland is cultivating a reputation as a state that lands especially hard on speeding truckers. The state's approach is not just to ticket truckers, but to send postcards to their employers notifying them that their drivers are speeding.

"The drivers might call it harassment," said state police spokesman William Ellery Clark. "We would just call it specific attention."

Led by trucking lobbies, and fueled by skepticism over whether there is an energy crisis, 20 states have reduced speeding penalties in the last 18 months. But police officials said there has been no such move, and no rumors of any such move, in Annapolis.

Similarly, officials said, there has been no discussion in Annapolis of laws to ban devices that can detect police radar. Virginia and Mississippi have such laws, and both states report improvement in speed limit compliance as a result.

Although Maryland CB radio buffs constantly warn each other about Mother Goose and Company, she and her unconventional friends are still proving effective. "You'd be amazed how many we still nab this way," said Clark.

"But it's much more than any one approach. In Maryland, the word is out that we really work the roads. And we make fair arrests. We tell our people we want to make 'good' arrests.

"A lot of people say 'So what?" about speeders. They say, "The hell with it; let them kill themselves.' But they're not just killing themselves.They're killing innocent victims.

"Mother Goose is just symbolic. But I'll tell you, when they come into Maryland, that pack slows down."