A year ago, Ray Peck and his family were driving across the Bay Bridge when a car slammed into the rear of his BMW, shoving it into the car ahead.

His car was devastated; the damage came to more than $7,800. But Peck and his wife suffered only minor injuries and their eight-month-old daughter was unharmed.

The two adults were wearing seat belts and the infant was protected by a child-restraint harness. Thanks to the seat belts, Peck says, he and his family did not become additions to the nation's highway casualty figures.

Today, Peck is the director of the National Highway Traffic Safety Administration, appointed by President Reagan. In another month or two, he will make a decision on whether to alter or throw out a long-delayed safety standard requiring major car manufacturers to install air bags or so-called automatic restraining belts -- the kind you don't have to buckle up -- in passenger cars.

Although Peck says he has not prejudged the issue, he has serious doubts about whether the automatic belts being designed by the auto companies should be required.

The controversial safety standard is a potent symbol of the administration's philosophical quarrel with many federal regulations.

In a campaign tour through Detroit last fall, Reagan said the auto industry was being virtually "regulated to death," adding that auto safety "is far more dependent on the quality of our highways and getting drunk drivers off the road" than on safety equipment mandated by federal regulators.

Murray Weidenbaum, chairman of the president's Council of Economic Advisers, says the result of the original NHTSA rule was to raise the cost of seat belts and thus the price of cars in order to protect people who don't want to protect themselves.

"Why the hell force us to design something that doesn't give [the motorist] a choice?" said GM vice president Frank J. Winchell recently, voicing a common auto industry complaint. "If you're that interested in saving lives, why not take him on directly" by passing laws requiring motorists to wear seat belts?

But to the insurnace industry and consumer activists who have campaigned for stronger regulation for a decade, Peck's decision is a key test of whether the administration means to weigh the costs and benefits of major regulations fairly, or tilt the outcome toward industry.

The passenger-restraint rule already has one strike against it. The Reagan administration suspended for one year the first phase of the rule on April 6 as one of several regulatory changes to help the auto industry. The delayed provision would have required installation of air bags or automatic belts on all large cars after Sept. 1.

Now, Peck is considering two alternatives for phasing in the rule and a third option, killing it outright.

Attorneys for State Farm Mutual Automobile Insurance Co. recently charged that the administration ignored a major survey by one of the Transportation Department's chief outside consultants that supported an automatic seat-belt standard. The administration, however, the study was considered.

And Rep. Timothy E. Wirth (D-Colo.), chairman of the House consumer protection subcommittee, pointing to criticism by several top officials, questions whether the administration has already decided the issue, making Peck's current rule-making a "charade."

Until last year, the air-bag system was the center of the debate, since that was to be the chief means of "automatic" passenger protection. Now, however, the major auto companies have decided not to offer air bags as an option and the focus is on so-called automatic belts.

The automatic belt is meant to overcome the plain fact that most auto drivers and passengers don't wear the manual belts that are required equipment in all cars today.

The most effective version of the automatic belt, available as an option on Volkswagon Rabbits, has a single shoulder strap running from each door to the console area between the front seats. A motorist slides behind the belt and when the door is shut, the belt is in place across the motorist's chest. An ignition interlock prevents the belt from being released until after the car has been started. A padded panel beneath the dash at knee level prevents the driver or passenger from sliding underneath the belt in a crash.

NHTSA surveys show that 89 percent of motorists owning the Rabbit with the automatic system use the belt, twice the percentage for Rabbits with conventional belts. Only 10 percent of all motorists wear manual seat belts, according to NHTSA.

In the General Motors Corp. version, formerly offered on Chevette subcompacts, a shoulder and a belt strap lead from each door to the console area between the seats and no knee pad is provided.

On some Toyotas, an electric motor brings the upper end of the shouler strap in place across the motorist's cheek once the door is shut.

If the belts remained locked in place when the door was shut, then they would indeed be "automatic" and there would be no debate for Peck to sort out. w

An effective automatic seat belt, restraining motorists whether they liked it, would save hundreds of lives and prevent thousands of injuries each year, all sides agree.

The savings to society -- in lower insurance premiums, lower hospital bills and Medicare payments, not to mention the saving of lives -- would overwhelm the costs involved in equipping cars with new belts.

But the debate isn't that simple.

Peck's agency has recognized that automatic belts must have a quick-release mechanism to permit rescuers to free an unconscious motorist from a car after an accident, or to permit a driver to escape from a car submerged in water, for instance.

"It has to be detachable," Peck said in an interview, "and we are right back to where we are now, trying to persuade people to use it." However Peck decides to regulatory issue, he will push an educational campaign to increase voluntary seat belt usage.

The issue turns on the design of the release mechansim. According to State Farm and consumer group representatives, the way that GM and Ford Motor Co. have answered the problem may have killed the automatic belt by stacking the cost-benefit analysis in favor of existing, manual belts.

Until this year, one of the systems designed by Detroit, would have provided the belts with a release lever, which, when pushed, would allow two or three more feet of belt to reel out, giving a motorist enough slack to wriggle free.

Then abruptly, Ford and GM changed their minds this year, saying that instead, they would add a buckle to their automatic belt designs just like the buckle on manual belts.

That, complained State Farm, would not only allow a motorist to escape in an accident, it would permit car occupants who object to seat belts simply to detach the automatic belt.

Result: no real difference between manual belts and the planned automatic belts.

To aid their campaign for an automatic belt requirement, a group of auto insurance companies hired Robert Nordhaus, a regulatory expert and member of the Council of Economic Advisers under President Carter.

Nordhaus prepared a study contending that the administration's one-year delay of the standard would allow 6,400 additional fatalities per year and 120,000 more moderate-to-critical injuries.

Counting the "cost" of a lost human life at $480,000, and figuring the range of expenses caused by traffic injuries, Nordhaus calculated that the total cost of the delay would be $30 billion -- equivalent to the loss society would have suffered if a vaccine had never been invented for tuberculosis, he said.

But Nordhaus was assuming a high usage rate for automatic restraints.

NHTSA, in defending the delay, countered that with the decision by GM and Ford to add conventional release buckles to their automatic belts, the actual usuage would be low, not much more than the usuage of manual belts.

". . . It is likely that a large percentage of motorists would adopt this usuage pattern and detach the automatic belts," NHTSA said in response to Nordhaus.

If 15 percent of motorists left the automatic belts in place, about twice the rate for manual belts, the numbers of lives saved would be "only" 75, NHTSA's analysts concluded -- not the significantly higher figure Nordhaus cited.

That tips the cost-benefit analysis against the automatic belts, NHTSA analysts said.

In a May 26 letter to Transportation Secretary Drew Lewis, who must approve Peck's decision, Wirth challenged the NHATSA analysis on almost every point: Why did the agency use GM's system, which the agency acknowledges is "poorly designed," as the basis for its conclusion that most motorists would detach the automatic belts? Why didn't NHTSA base its analysis on the experience of VW Rabbit buyers?

Although the Rabbit gets the highest marks, one-fourth of the owners said in the same NHTSA survey that they probably would not use the system if it weren't connected with the ignition. (NHTSA is forbidden by Congress from requiring such interlocks; VW voluntarily installed it on its belt system.)

Could Detroit design a reasonably comfortable automatic belt with a safety release to fit practically all emergencies? Of course, says Brian O'Neill of the Insurance Institute for Highway Safety, a leading advocate of automatic protection.

Could Detroit design and mass produce an air bag within the budgets of most motorists? Undoubtedly, O'Neill insists.

But the car manufacturers say that most motorists don't want such protection and the industry won't risk forcing it on them.