Prince George's County is providing free parking lot security and traffic control for the profit-making, privately owned and operated Capital Centre in Largo at a cost of more than $120,000 a year to county taxpayers.

The figure represents salaries for as many as two squads of county police who regularly are assigned to the 8,000 car parking lots and access roadways that cut through the 60-acre tract of public parkland.

The police detachment operates from a "command center" inside the area, complete with radio dispatcher equipment, a soda machine, finger printing facilities and a holding cell.

In addition to the county police contingent numbering up to 24, as many as half a dozen county park police on arena. Hugh Robey, Prince George's parks director, estimated the annual cost of salaries for the mounted police at about $40,000.

The center was built seven years ago and has become the region's primary indoor site for major sports events, rock cocerts and exhibits. During its inception, construction and operation, it has been closely identified with the political and governmental leadership of the county, so much so that it has taken on the image of a quasi-public institution in some people minds.

Its attorney is Peter F. O'Malley, a leader of the county's Democratic Party, while Abe Pollin, owner of the center, is a fund-raiser for Maryland state Senate president and gubernatorial candidate Steny H. Hoyer (D-Prince George's.)

The arrangement for county police protection of the private enterprise is now in its fourth year. With both fanfare and controversy nearly five years ago, county officials agreed to turn over the parkland to the venture and also spent $2 million in public funds to build internal access roads and a sewage treatment plant.

The special police protection came later, with relatively little publicity. Its initiator, Police Chief John W. Rhoads, contributes to defend the arrangement as a legitimate use of police power.

"It is easier for us to assign the center to a group of individuals," Rhoads said this week, than "to come in after the fact, to mobilize our street forces and then move in en masse. We were at a tactical disadvantage."

In fact, Rhoads said, "The Capital Center's complaint to me is that we understaff compared to other facilities around the country."

Capital Center security chief Barry Silberman said yesterday he was "satisfied" with police protection afforded the 20,000-seat erena.

Silberman spoke to a reporter before departing for the National Basketball Association playoffs at the Philadelphia Spectrum, a privately owned arena built on private property. Its parking lots, however, are city-owned. According to Stephen Flynn, the SPectrum's security official, the parking concessionare hires a private security firm to patrol the lots.

The District's Robert F. Kennedy Stadium and armory are city-owned. Their parking facilities are on land owned by the National Park Service and patrolled by U.S. Park Police. The tab, however, is paid by the sponsor of each event.

"If you're taking money in for something, you have an obligation," said Robert H. Sigholtz, general manager of the 105-acre "Starplex" (stadium-armory) facilities. "It's part of the promoter's obligation. That's the way we look at it."

In Prince George's County, they look at it differently. 'This is one of the few places in the county that develops the numbers of people and autos at any single given time," said Rhoads.

"No matter what happens, whenever there are 20,000 people, there's going be a need for police,"said Rhoads. "We'd rather be pro-acive than reactive."

To deal with what Rhoads called a "goodly number" of stolen cars, stolen auto parts and larcenies from cars in the early days of the Capital Centre, the county's special operations deivision, based one Beltway exit away in Forestville, was assigned the arena detail.

At first, Rhoads said, the police were posted on the arena roof "scanning out until the parking lot incidents were reduced."

Additional problems rose, Rhoads said, during the rock concerts, and county police were on hand to move inside if needed to supplement the arena's own internal security force.

Times change, however, and Rhoads said he is now considering reducing the Capitol Centre contigents, especially for events like tennis matches and the circus. Traffic is moving more smoothly, too, he said. "Most of the people are repeaters and are beginning to move in and out very well," he said.

A Washington Post request last week for information regarding the police role at the Capital Centre generated a police staff meeting and a flurry of intra-office memorandums. A two-page summary noted that the center was charged $6,382.58 extra for additional expenses or personnel required on seven occasions since the Grand Central Station rock concert resulted in $320 in damages to police vehicles on Aug. 8, 1976.

Attached to the summary were five pages of policed events dating back to a May 4, 1975 "Walk-a-thon" at Potomac (Prince George's County) Senior High School patrolled by two officers for five hours.

Lt. D.W. Downs, tactical commander of the special operations unit, reported that his men made 1,556 shopping center checks consuming 1,123 manhours from December through March.

Extra officers detailed at shopping centers during last Christmas season cost $39,338 in salaries, Rhoads said.

The fact sheet underscored its point: It is the policy of this department to provide police officers at any large gathering in the county, wherever possible and where it is determined to be in the best interest of public safety."

School athletic contests evidently are an exception. "We send officers on overtime to these events" at the school's expense, said police spokesman John Hoxie. "This is consistent because the chief feels they [the policy] are not necessary."