The carpooling restrictions on Interstate 66 have taken the rush out of rush hour for a relative handful of motorists who use it then and pushed the highway's biggest traffic surges into the hours immediately after the conventional morning and evening rush periods.

In a dramatic reversal of traffic patterns on other Washington area highways, traffic use on the new 10-mile roadway jumps by more than four times in the hour following each peak period, figures released yesterday by the Virginia highway department show. These surges apparently are the products of lone motorists who schedule their driving times to avoid the regulation--dubbed High Occupancy Vehicle-4 in bureaucratic parlance--requiring cars to carry four riders during rush hours.

According to state traffic figures completed during the week beginning March 14, an average of 8.7 vehicles per minute passes a given location along the roadway during rush-hour periods, which are defined as 6:30 a.m. to 9 a.m. inbound and 3:30 p.m. to 6:30 p.m. outbound. The same location, the figures show, is passed by about 39.5 vehicles per minute in the first hour following the morning and evening rush.

Local elected officials, angry at what they perceive as the road's underuse, said the figures point out the need for changes in carpooling restrictions for the three-month-old highway. "We think it's totally ridiculous not to get better usage out of that road," said Fairfax supervisor Nancy Falck of Dranesville.

Highway officials defended both their figures and the carpooling rules, saying that motorists have not yet had enough time to organize themselves into carpools.

"We expected to see growth in carpooling over an extended period," said David Gehr, assistant division administrator for the Virginia Department of Highways and Transportation. "I don't think this time frame is a valid time frame to see whether it's going to encourage carpooling. I think you've got to wait a while."

Gehr said the department has no plans to change the HOV-4 rules, and said he expects carpool growth on I-66 to match or exceed that on the similarly restricted lanes of I-395, which opened in 1973. A 1974 survey of Shirley Highway's restricted lanes found about as many vehicles as are now using I-66, according to state highway figures. A 1982 survey found that number had more than quadrupled.

Despite the post-rush-hour traffic bulges on I-66, airborne traffic spotters for local radio stations report that traffic on the roadway has continued to flow steadily and tie-ups have been minimal. The average number of vehicles per minute on I-66 is 39.5 during its peak periods just after rush hour, compared to peak period usage more than twice as high on the three southbound unrestricted lanes on Shirley Highway during the afternoon rush.

Virginia state police recently have been issuing tickets and warnings to lone morning motorists who park on the shoulder of I-66 outside the Beltway, where there are no rider restrictions, to wait for 9 a.m. Police say some motorists also are pulling over on surface streets adjacent to the highway's entrance ramps to await the 9 a.m. rule change.

Yesterday's highway figures, the first official count of traffic on I-66, seem likely to add to the dispute about the highway's future. Arlington residents have fought for stiff restrictions on its use, in an effort to limit traffic noise and pollution, while residents of the outer counties have sought a restriction-free roadway that would speed their journeys into Washington.

" The figures show us that the only way this region is going to work is if people car pool, van pool and use public transportation," said Ellen M. Bozman, Democratic chairman of the Arlington County Board. "If you've got that many people who wait to use the roadway until after the HOV restrictions are lifted, imagine how many would flood on if there were no restrictions."

U.S. Rep. Frank Wolf (R-Va.) who has helped negotiate the lifting of HOV-4 restrictions on two Rosslyn-area I-66 ramps, said the figures confirmed his belief that the roadway's restrictions should be eased at least to allow three-person carpools.