A National Academy of Sciences panel said yesterday that the federally imposed 55-mph speed limit saves between 2,000 and 4,000 lives annually and should be retained for most highways, but it tossed to Congress the question of whether higher speeds should be legalized on rural sections of the interstate system.

Congress ordered the study late in 1982 to put out a political fire generally between westerners who wanted to drive faster and easterners impressed with the reduction in highway fatalities that lower speeds had brought. The controversy was threatening to slow down progress on the highway construction bill that raised gasoline taxes by 5 cents a gallon.

The report, by the Transportation Research Board of the National Research Council, will not end the debate. Panel chairman Alan Altshuler said in a briefing yesterday that the question of permitting higher speeds on well-designed expressways in rural areas is essentially a "value judgment" that has to be made by Congress. His 19-member committee could not reach a consensus, he said.

It did agree, he said, that if speeds of 60 or 65 were permitted on rural interstate highways -- about 31,000 miles of the 42,500-mile interstate system -- about 500 more people would die each year in motor vehicle accidents and taxpapers would pay about $10 million more for government programs affected by death, disability or injury.

"On the other hand," the report said, "about 850,000 hours of travel time would be saved for every life lost. This means that about 100 years of travel time would be saved in exchange for the loss of an additional life, plus an additional serious, severe or critical injury."

Diane K. Steed, head of the National Highway Traffic Safety Administration, which financed the panel's work, said she is pleased that the report recognizes the life savings of the lower speed limit and said the agency is studying the report's recommendations.

The 55-mph limit was imposed in 1974 as an energy-saving measure in response to the Arab oil embargo. But in that first year, highway fatalities decreased by 9,100 -- the largest drop since gasoline was rationed during World War II -- and the 55-mph limit started to be viewed as a life saver as well as fuel saver.

The Republican platform in 1980 proposed eliminating a nationally mandated 55 limit, but the platform was silent on the subject this year. Much impetus for the turnaround came from the West, where higher speeds are a way of life, and part of it came from a philosophical objection to a federal role in setting speed limits, which had previously been a state prerogative.

The panel said the federal government should continue to set maximum speeds. It also reported widespread public support for the limit in all sections of the country, according to polling by the Gallup organization. The least support comes from the South, where 70 percent favor a 55-mph maximum.

Current law requires the Federal Highway Administration to withhold some federal highway money from states in which more than 50 percent of all motorists exceed the speed limit.

The study says 37 of the 50 states would not have met the 50 percent requirement last year without adjusting their averages through complicated formulas "that we don't think have much validity," Altshuler said. All the states ultimately met the requirement.

One of the problems, the panel said, is that speed-monitoring systems make no distinction between a motorist going 56 and one going 80. It recommended a point system that would weight speed violations by degree and road type. Under this system, an automobile doing 60 on a high-crowned two-lane highway with no shoulders would cost the state more than one doing 60 on a four-lane interstate, which might persuade the states to stress enforcement on the less-traveled but more dangerous two-lane highways.