Automobile will continue to dominate American passenger travel and transportation problems for the balance of the 20th Century, according to a broad study released yesterday by Secretary of Transportation William T. Coleman Jr.

If current government policies are not changed, he warned, major urban areas face destruction and the highway system itself will not be able to attain the 55-miles-per hour speed limits of today.

Even if passenger travel by all other forms of tranportation were to double by 1990, which Coleman said was possible, autos still would account for 80 per cent of all intercity travel. Truck traffic also will increase sharply without policy changes, he added.

Currently, autos account for 92 per cent of all intercity passenger miles traveled, compared with 5 per cent for the airlines, 2 per cent for buses and 1 per cent for railroads and water travel combined.

In the freight business, Coleman projected a 72 per cent increase in tons shipped by privately owned trucks and 70 per cent for regulated interstate truckers, from 1975 to 1990.

Although railroads dominated the freight business through World War II, the rail share of intercity tonnage is now down to about 30 per cent compared with 20 per cent by inland barge, 32 per cent by truck, 18 per cent by pipelines and less than 1 per cent by airlines.

"By sparking the growth of the highway system, the automobile has had a major impact on the movement of goods . . . It has been the primary source of our umparalleled personal mobility and a shaper of our environment, industry and culture," Coleman said.

Whether for good or ill, he added, all current methods of transportation and all proposed for the future will be judged in terms of their cost and convenience characteristics relative to the personal automobile.

Coleman's conclusions about the automobile and the challenges it presents to future government officials were included in a 412-page report on national transportation trends and choices to the year 2000, the first study of its type ever published by the federal government.

While much information in the document is not new, Coleman's report represents a first attempt at gathering such data in a single document. At a news conference yesterday, Coleman termed the report "an important part of my legacy," which he hopes will be used as the basis for further building of a better transportation system.

"The time is clearly past when it is possible or even acceptable to deal with transportation on a piecemeal basis," said Coleman of this nation's current approach to transportation, which involves looking at individual industries one at a time. A prominent example is the government program ton rehabilitate bankrupt railroads in the Midwest and Northeastern states.

Coleman's report was prepared over the past year by a staff under Assistant Secretary Robert Binder. A DOT spokesman said it cost less than $100,000 and was prepared almost entirely inside the agency without outside consultants.

According to the study, U.S. spending for transportation now equals one-fifth of the annual gross national product and all indications are that demand for transportation services will continue to mushroom. The document pinpoints what will happen to different regions of the country with a 15 per cent population growth and a projected 87 per cent gross national product growth between now and 1990, in terms of freight and passenger movement.

Overall, he forecast a 50 per cent gain in passenger miles traveled and a 70 per cent increase in freight ton miles in the next 15 years.

this points to a potential crisis of energy supplies but Coleman said new policies - aiding urban trassit, requiring more "socially responsible" autos, establishing separate highway lanes for trucks nd encouraging long-distance freight shipping by rail - could actually decrease the share of energy now consumed by transportation.

Petroleum products now account for 95 per cent of energy used to operate transportation; American transportation uses more than half the annual petroleum consumption in this country.

The nation currently has 3.8 million miles of highway covering 33,000 square miles of land - a little less than the State of Indiana.

One major currently to be faced, Coleman said, is the price Americans pay for auto mobility in terms of death and injury. In 1975, an estimated 46,000 Americans lost their loves in motor vihicle accidents, accounting for 44 per cent of all accidental deaths and for 38 per cent of all deathas among 15-to-20 year old males.

Coleman recently recommended that auto manufacturers take part in an extensive demonstration program of the life-saving capability of passive restraints - air bags that inflate instantly upon crash or seatbelts that lock in an instant. He is expected to announce next week that at least two automakers have agreed to such a program.

Among other conclusions in Coleman's study:

Amtrak, the national rail passenger corporation, should be subjected to a new policy look. Coleman said current federal subsidies are not worthwhile on most routes outside dense urban corridors, because of few people ride trains. But the nation might want to maintain the system as an insurance policy in the event of another petroleum shortage, he added.

users of various freight transportation systems should pay the costs involved, a proposal which would alter radically the inland waterway industry by establishing user charges for facilities financed by the federal government and which could result in new user charges for truckers.

Improvements in the rail system likely will have an important impact on future evolution of the trucking and inland barge industries, mainly by slowing down increase shares of tonnage among rail competitors. The changes also will make multimodal rail-truck movements more attractive for longer distances.

A resurgence of air travel is implied in the data on increased affluence ind travel and supersonic airliners may become a standard for cross-ocean travel. A future market opportunity will be for short-distance air service using quiet, short takeoff-and-landing craft.

Coleman took a parting shot at Congress yesterday, at the press conference called to unveil the new study. He accused some legislators of displaying "arrogance" in proposing restrictions on oil tankers operating 200 miles or more off the U.S. coast.

"The faci is that the ocean is owned by all the people of the world," and Congress is forgetting some of the lessons of Watergate and Vietnam in assuming that the U.S. can dictate world policy, he said.

The section in Coleman's report dealing with oil spills, written before a recent rash in U.S. waters, calls for increased federal standards - particularly for the relatively small number of such accidents that account for most of the oil spilled. Of all oil pollution accidents, 70 per cent of the volume of spills resulted from hull, tank, pipeline or pipe system ruptures and leaks but accounted for only 12 per cent of all accidents.