Sen. Roger W. Jepsen (R-Iowa) has found a new way to beat Northern Virginia's rush-hour traffic: congressional immunity.

The senator, who lives in Alexandria, avoided $35 in fines Friday morning when he invoked immunity provided by the Constitution and told a police officer he could not be arrested for driving alone in the restricted Shirley Highway carpool lanes because he was enroute to Capitol Hill.

"The senator said, 'I understand I'm permitted to use these lanes,' and the policewoman walked away and got back in her car," said Jepsen's press secretary, James Lafferty. "This was no major constitutional crisis." The officer wrote no ticket despite the much-debated HOV-4 rule that restricts traffic on the express lanes and portions of I-66 to vehicles with four persons during rush hours. Until disclosure of Jepsen's commuting, the only other group of Washington workers who were known to be avoiding the carpool restrictions were diplomats who also have claimed immunity.

Arlington Police Chief William Stover said yesterday that the officer who stopped Jepsen acted properly. Stover said that when a member of Congress is on his way to or from a congressional session he is exempt from enforcement of traffic laws.

"Of course, if he were endangering public safety, like being intoxicated, then we're going to arrest him," Stover said. "But commuter lanes, you're talking about something else. Whether there's four people in the car or one doesn't endanger the public."

The issue of congressional immunity has become controversial in recent weeks since Rep. Louis Stokes (D-Ohio) was stopped by Montgomery County Police for three alleged traffic violations and released after police learned he was a member of Congress.

Since then, law enforcement officials in the District of Columbia, Alexandria, and Montgomery and Prince George's counties have stated that members of Congress are no different from other citizens when it comes to traffic tickets.

Lafferty said he did not know which law enforcement agency had stopped Jepsen, and spokesmen for both the Virginia State Police and Arlington Police, which patrol the highway, said they were not aware of the incident. CAPTION: Picture, SEN. ROGER W. JEPSEN . . . avoided $35 in traffic fines