If the Russians aboard the Soviet intelligence ship that lurks off the Virginia capes lose track of the U.S. Navy ships here, they can tune in highway traffic reporter Al Basnight's twice-daily traffic reports on local radio stations.

For 10 years Basnight has explained the ebb and flow of Tidewater traffic, and more often than not, his explanation has been the U.S. Navy, Norfolk biggest employer.

When the traffic was unusually light one morning, Basnight announced: "The ships are out at sea. Looks like smooth sailing for us landlubbers."

When the roads were clogged another day, Basnight cautioned: "You'd better leave for work about 15 minutes early. Three aircraft carriers have pulled into port and you wouldn't believe the mess."

The concentration of military personnel here -- enough to make the difference between a good rush hour and a bad rush hour in an area of more than a million people -- attracts the keen interest of Soviet intelligence agents, officials from the FBI and military investigative agencies say.

Norfolk is home to the largest naval complex in the world, spread out here in a semicircle of four major bases and encompassing activities that range from summer training for midshipmen to honing the skills of sailors assigned to the Navy's fleet ballistic missile submarines.

That makes this area a virtual treasure chest of military secrets for the Soviets, according to FBI officials and the Naval Investigative Service.

Accused spies John A. Walker Jr., his brother, Arthur, and his son, Michael, allegedly mined a number of Naval activities here for classified data that some Navy officials say may have helped the Soviets improve their submarine warfare capabilities.

Navy and FBI officials here long have recognized that Norfolk would be a prime target for Soviet espionage. An agent in charge of the local FBI office publicly expressed alarm over the prospects for espionage about 10 years ago and urged a crackdown.

Navy activities now answer their telephones with the statement that "This is not a secure line," and oldtimers here say access to the bases is tighter than it used to be. Security people make more frequent sweeps of offices at the bases, looking for classified documents that should be locked in approved safes.

They are backed up by 97 special agents of the Naval Investigative Service, which maintains its biggest office here.

But given the plethora of classified messages -- any ship movement is automatically classified by the Navy even if the ship is moving from one base to another -- and the abundance of Xerox machines, some commanding officers say the opportunities for disloyalty are unlimited.

The last public reminder of that came in 1982, when Petty Officer 2nd Class Brian P. Horton, assigned to a European intelligence command here, was accused of offering the Soviet Embassy in Washington information on the United States' master war plan for $3,000. Horton was sentenced to six years in prison.

One-sixth of the U.S. Navy works here -- enough sailors to require the Navy to assign chief petty officers full time to Norfolk's traffic and criminal courts to assure that Navy defendants show up in court; enough to lead used car dealerships to put up signs like "Welcome Home Nimitz" when the big carrier returns home, and enough to provoke sailors themselves to complain in polls taken by Navy Times newspaper that the city is "too military" and has "too many ships."

Fully a fifth of the Navy's 500 ships are home-ported here. That includes the majority of every major type of ship in the Atlantic Fleet except for ballistic missile submarines -- including attack submarines, guided missile cruisers, aircraft carriers, amphibious ships and destroyers, as well as the Atlantic fleet's only active battleship.

In fact, so many ships can be found in Norfolk that Navy Secretary John F. Lehman Jr. has warned that some should be moved to other ports to lessen the Navy's vulnerability to a surprise attack.

While the Navy here is divided into four major bases, the bulk of activity takes place at at Norfolk Naval Base. NOB, as the sailors call it, (short for Naval Operating Base) is a minicity big enough for its own police force, two gasoline stations, four chapels, two 24-lane bowling alleys, eight softball fields, a giant supply center billed as the world's largest department store, and what will soon be three fast food restaurants.

Overseeing the sailors and ships is one of the Defense Department's major unified commands, CINCLANT, or the Navy's Atlantic command.

Presided over by a four-star admiral, this command works out of an unimposing compound of squat red brick buildings, once a military hospital.

Navy officials say the compound, where accused spy John Walker worked for six years, constitutes a nerve center for the Navy that is second only to the Pentagon. Besides the command of of the Navy's Atlantic Fleet, it houses the command of all U.S. forces -- Navy and otherwise -- assigned to the Atlantic and the Atlantic forces for NATO, whose separate building is distinguished by the black limousines in the driveway and the three-foot high missile-shaped markers that edge the sidewalks.

While the Navy dominates Norfolk, there are other lures here for Soviet agents: the Central Intelligence Agency is not far away with Camp Perry, which poses as a Defense Department installation but is known internationally as "The Farm." The Air Force operates a giant base of its own, Langley AFB, in Hampton, home of the Tactical Air Command, and the Army has a training headquarters and a transportation testing base.

To support the immense military establishment, nearly a thousand defense contractors maintain offices in the region, including VSE Corp., which employed Arthur Walker. He is accused of passing VSE documents on Navy ships to the Soviets. The biggest shipyards in the country are here, including Newport News Shipbuilding and Dry Dock Co., the only shipyard big enough to build aircraft carriers. That yard and a government-run one in Portsmouth contain sensitive design and repair facilities that work on nuclear-powered submarines.

It was in Norfolk that John Walker, arrested May 29 on espionage charges and believed to be the head of the espionage ring, spent much of his career. He worked as a communications officer in the Atlantic Fleet Headquarters between 1967 to 1969 and 1974 to 1976. He was assigned first to the prestigious submarine command known as "SUBLANT," then to an amphibious forces command, and then to the surface forces, known as "SURFLANT."

While his posts involved very little decision-making, they should have given him wide access to sensitive material, including communications with the nation's submarine force and probably the highly restricted reports of American intelligence on the operations of Soviet submarines.

He was cleared to handle top-secret messages and highly trained in the operation of the Navy's crpytographic system that scrambles radio messages into unintelligible garble.

Navy officials decline to discuss security measures here except in the broadest of terms.

Retired officers say Walker could have done the most damage from 1967 to 1969 when he was assigned to the SUBLANT staff.

Submarines are considered in some ways to be the most valuable of U.S. nuclear forces because they are hard to detect and the only force expected to survive a nuclear attack.

If Walker passed information to the Soviets about the suspected location of their submarines, "They could have formed a better idea of how good our system worked than we have ourselves," said retired Adm. Eugene Carroll, with the Center for Defense Information.

In addition, some Navy officials fear, Walker, and his alleged associate Jerry Whitworth in California, also a communications expert, might have passed enough information for scrambling messages to enable the Soviets to break the Navy's cryptographic code and decipher electronic signals that their spy ships routinely pick up.

"Cryptographic material, that's the keys to the kingdom," said Carroll. "There is nothing more sensitive."