The prospect of twin-trailer trucks, 102 inches wide and up to 70 feet long, barreling along Leesburg Pike near Tysons Corner has upset Northern Virginia officials who are preparing to protest recently issued federal regulations allowing longer, wider trucks on primary roads throughout Virginia.

"It's totally ridiculous from our standpoint," said Fairfax County Transportation Director Shiva Pant, whose recommendations will go to the Board of Supervisors May 2. "We don't have the capacity for these things, we don't have the turning radii they need. Our roads are just not big enough to accommodate them."

The state is conducting a series of 10 public hearings in the next six weeks to gather opinion on new federal regulations, issued April 6, opening up 1,544 miles of primary roads throughout the state to big trucks. A hearing in Northern Virginia has been set for May 3 at the Falls Church City Hall.

In Northern Virginia the primary roads affected include Lee Highway (Rte. 29) to the Arlington Boulevard (Rte. 50) intersection, Rte. 50 to the Leesburg Pike (Rte. 7) intersection and Route 7 from Winchester to the Shirley Highway (I-395). Under the federal definitions, these roads are now open to 102-inch wide trucks with 48-foot single trailers or with two 28-foot trailers. No restrictions are placed on the length of the truck cabs.

Last winter, Virginia, along with most other states, reluctantly went along with a provision, tagged onto legislation increasing the federal gasoline tax by 5 cents, that allowed the big trucks on interstate highways. Virginia added another 183 miles of contiguous primary roads to allow the trucks ways to get on and off the highways.

But on the day the new law became effective, the U.S. Department of Transportation added more routes, arguing that Virginia, like other states, had been overly restrictive. Those new routes may be amended after the state completes its public hearings this summer.

"We were somewhat concerned that we didn't have any prior warning," said William Landsidle, assistant deputy at the Virginia Transportation Department, shortly after the new rules came out. "Very few people were aware of what had happened."

Virginia is awaiting a federal court ruling in cases brought by Pennsylvania, Vermont and Georgia, seeking permanent injunctions against the federal government's trucking rules, said Landsidle yesterday. Barring a favorable ruling, Landsidle said Virginia expects to appeal at least some of the additional truck routes later this year.

The new routes have already stirred groups that have long opposed any relaxation of Virginia's own truck limits, which are 55-foot lengths and 96-inch widths and are still applicable on secondary roads.

Ray Ashworth, executive vice president of the Virginia Highway Users Association, said few trucks have taken advantage of the relaxed restrictions, adding that the likelihood of twin-trailers on smaller roads is slim.

Ashworth said the state's original plan, allowing only one-half mile access to big trucks off the interstates, was "ludicrous.

"You couldn't get anywhere; you'd have to have a helicopter," he said. "I don't think anyone could say Virginia was being reasonable."