IN COLLISIONS, some cars give substantial protection to the people riding in them. Other cars do not. If you are buying a car, you might like to know which is which. The federal government, through its National Highway Traffic Safety Administration, has been systematically testing cars and collecting accident data for several years. Now it has published, in a pamphlet called "The Car Book," a clear and revealing summary of the results. This booklet, with its ratings and statistics, is a major contribution to the reduction of highway death rates.

Last year, 54,000 people died in automobile accidents and, unlike most of the other death rates, this one has been rising in recent years. Better design is getting more important as cars get smaller and lighter.

All new cars sold in this country must be able to withstand a head-on crash at 30 mph without serious injury to the occupants -- as long as they wear their seat belts. NHTSA has been crashing cars at 35 mph to see which models offer greater protection. The results are instructive, but no one test alone tells everything about a car's safety. The booklet also includes the actual road performance -- the number of people killed in cars of each make and size, for the model years 1974 through 1977, in relation to the number of those cars in use. The buyer can see which manufacturers' cars have had good safety records in the past, and which have not.

Only six cars fully passed the crash tests -- a neatly impartial balance of two General Motors cars, two Fords and two Chryslers. A Fiat passed the most important part, the protection of the occupants. The Japanese cars have not done at all well on these safety tests, and the Japanese companies may wonder whether a subtle form of protectionism is operating here. But there's no evidence of it. And if the tests are adverse to the imports, they are also an invitation to the healthiest kind of competition -- in contrast to the import quotas that most of the American auto industry would prefer.

There is no question that present technology can build cars far safer than any now on the highway. The Department of Transportation has developed a car that can protect its occupants in a head-on crash at 50 mph -- a standard far beyond any model now in production. That prototype, incidentally, is not a tank. It looks like a sports car and goes 29 miles on a gallon of gasoline.

"The Car Book" should appeal to anyone -- for example, the next president -- who prefers to inform the buyers, rather than regulate the manufacturers.This little book sets an invaluable precedent. If it appears in annual editions, at the same time that each year's new models go into the showrooms, it will do more than surgeons can to save lives on the road.