RICHMOND, JAN. 28 -- Virginia moved closer today to raising the speed limit on rural portions of its interstate highways to 65 miles an hour, an action that already has been adopted by 38 states.

The legislation, which has the backing of Gov. Gerald L. Baliles and the General Assembly's Democratic leadership, would retain a 55 mph limit on trucks. It would take effect July 1. The legislation still must pass the full House and Senate, but today's 13-to-7 approval by the House Roads Committee was a key hurdle.

The higher speed limit would apply to 789 miles of interstates in Virginia, including:

I-95 south from Rt. 610 (Cardinal Drive) in Prince William County, for 69 miles, to the Hanover-Henrico county line north of Richmond.

I-66 west from Rt. 658 (Compton Road) in Fairfax County, for 51 miles to its termination in the Shenandoah Valley at I-81.

Virginia and Georgia are the only southern states that have not increased their speed limits since last April, when Congress permitted the states to lift the 55 mph limit on rural portions of the 42,500-mile interstate highway system. Urban areas were defined as those with a population of 50,000 or more.

Most of the states retaining the lower limit are in the Northeast, including Maryland, which has no legislation pending to increase the limits on its interstates. Because both of the District's interstates -- I-295 and I-395 -- are in urban areas, they would not be eligible; the highest speed limit in D.C. is 45 mph on I-295 (the Anacostia Freeway).

Congress imposed a 55 mph national speed limit in January 1973, in response to the energy crisis sparked by the Arab oil embargo. Before that, all speed limits were prerogatives of the states, and some had placed it as high as 75 mph.

A side benefit of the lowered speed limit was a decrease in highway accidents and deaths. A study prepared for Transportation Secretary Vivian E. Watts found that, as of last June, the average speed on Virginia's rural interstates was 59.9 mph, an increase of 3.6 mph over the previous year.

It concluded that raising the speed limit to 65 would result in six to 18 more fatalities and 171 to 405 more injuries per year in Virginia. On the other hand, it said increasing the average speed by 3 miles an hour would save 1.3 million hours in commercial and business travel time.

In December, a survey of 22 states by the National Highway Traffic Safety Administration reported that fatalities had increased by more than 50 percent on highways where the speed limit had been raised to 65 mph. However, officials cautioned that the numbers were for only a three-month period and that other factors could have influenced the increase.

In his State of the Commonwealth speech this month, Baliles said that "public sentiment clearly favors" the higher limit. If adopted, the governor said, "to ensure that 65 means 65, I will issue orders that the new speed limits should be strictly enforced." He also favored keeping the limit at 55 for trucks.

Watts said that "although some individual legislators oppose it, there is no strong objections or unified movement" to defeat it.

One opponent, Del. Mary A. Marshall (D-Arlington), predicted "it will mean increased fatalities, increased accidents and higher insurance premiums.

"I'm afraid what we're really doing is putting the speed at 75," adding that "I-95 is going to be a mess," because the speed limit will alternate between 55 and 65 from Washington to Richmond.

Del. C. Richard Cranwell (D-Vinton), an influential legislator who testified in favor of raising the limit, said "I'm not against safety, I'm for safety." He conceded that studies show that among the states that have returned to the 65 mph limit, four have reported declines in highway fatalities, while the others have posted increases.

"If safety alone were the criteria," he said, the limit should be lowered to 45 or 35. But he said the interstates, with limited access and wide medians, were "designed for speeds of 65 to 75."

Much of the debate during today's hearing concerned whether the speed limit for trucks and cars should both be raised to 65 mph. Adopting different limits would "increase car-truck conflicts," according to the state study.

Del. George Allen (R-Charlottesville) said a lower speed for trucks would present "precarious enforcement" problems for police. Cars and trucks will "all go the same speed anyway," said Allen, who said "truck drivers have been voting with their right foot."

However, L. Ray Ashworth, a lobbyist for the Virginia Trucking Association, supported the two-level limits. He said trucking company owners "feel 55 saves fuel, reduces maintenance and translates to lower insurance costs" by reducing accidents.