Prince George's Police Sgt. G.A. Hatton's wife won't ride with him in his police cruiser anymore, for fear she will not reach her destination.

It's not that the 14-year-veteran is a bad driver, but that Prince George's depends on him, like other officers who take their squad cars home for personal use, to give his spare time to provide adequate police service for county residents . . . even if it means abruptly dropping off his wife in the middle of a shopping trip to chase a criminal.

"The majority of the time she never got to where she was going because of an arrest or something," said Hatton, adding that his wife grew tired of leaving home for the supermarket and winding up at the police station instead.

In 1972, Prince George's was one of the first police departments in the country to institute a personal car program, allowing officers to drive police cruisers while off duty but calling on those who do so to respond to emergency calls they hear while in the cars. Today, with a per capita force far smaller than the national average, Police Chief John McHale says Prince George's could not handle the increasing demands for service without the program.

Across the nation, suburban counties have an average of two policemen for every 1,000 residents, according to statistics compiled by the FBI. Prince George's falls far below that mark, with only .8 county policemen for every 1,000 citizens. Fairfax and Montgomery counties also are far below the national average, with .82 and .79 officers per 1,000 residents, respectively, but Prince George's police handled about 350,000 calls last year, compared to about 200,000 in Fairfax and 220,000 in Montgomery.

Prince George's makes ends meet because off-duty officers riding in their personal cars answer nearly 10 percent of all calls for service, ranging from routine traffic stops to support for officers in trouble.

Off-duty Montgomery officers also answered nearly 10 percent of the county's calls last year. Montgomery officials say they don't depend on off-duty officers, but admit that without the program it would take longer to respond to calls in rural parts of the county. Fairfax County does not have a personal car program.

In Prince George's the personal car program is aimed at filling the gaps in a patrol force which normally amounts to 70 to 90 men on a given shift, stretched over the 500-square-mile county. (For several hours each day, when shifts overlap, the number of patrolling officers is higher.) The program is voluntary but an estimated 90 percent of the uniformed officers participate. While driving the cars off duty the officers must have the radio on, and they are expected to answer when a dispatcher puts a call "out for bids," or calls for any car in an area to respond to a crime.

The benefit for officers in the program is a second family car with free gasoline; the cost is being on call every time they get behind the wheel.

Officer Diane Duncan, who takes 12 to 14 off-duty calls each week, says her neighbors appreciate the shiny white car with the lights on top in her driveway.

"I think a lot of the neighbors feel safer, knowing you're there," she said.

But Laney Hester, outgoing president of the Fraternal Order of Police, contends that even with the personal car program, a shortage of officers leaves county residents with less police protection than they should have.

"What it translates into for the average citizen is more danger," said Hester, noting that while crime in the county has increased six percent since 1974, budget constraints have caused the number of county police officers to generally decline during that period.

County Executive Lawrence J. Hogan recently added 33 new positions to bring the authorized number of officers to 873, the highest number since 1977. As of last week, there were 838 officers on duty in the county. Hester contends that 75 to 100 more officers are needed to do the job in a county where one man might patrol a sparsely populated beat larger than the District of Columbia.

"I've actually heard the dispatcher ask: 'Any car for a robbery in progress?' and there's no answer," Hester said. "Here's a guy who has just had a gun stuck in his face, he thinks the police are on the way and they can't even raise a car!"

Neither Hogan nor Chief McHale agrees with Hester's assessment. Both say the number of officers in the force is sufficient to protect the citizens of the county, though McHale adds that additional officers could shorten the time it takes police to respond to calls.

"How much is enough?" asked Hogan spokesman Bob Hunter. "As long as there is one criminal on the street, there is never enough police protection . The question is a standard of reasonableness -- that's his Hogan's position."

Sgt. Hatton's squad of 10 officers patrols an 18-square-mile high-crime sector stretching from the District line to the Beltway between Suitland Parkway and Central Avenue. On most shifts, Hatton says, he has just enough people to respond to citizen calls within the three-to-five-minute county average.

But if an officer is ill, or others are tied up in court, holes show up in the coverage. On one such tour last week, for a few hours he and a normally desk-bound lieutenant had to patrol the streets themselves.

"I tried to get help, but when they punched it into the computer they said nobody was available," said Hatton.

So far the tight manpower situation has not resulted in any injuries to officers, according to Hatton. He said the lack of manpower to back up a policeman who gets into trouble makes most officers "a bit more cautious."

The thin coverage is most evident when action picks up late at night, when most off-duty officers are asleep. It is not unusual, police say, for calls to be stacked up on the dispatcher's computer screen for want of an available cruiser, on or off duty, at these times.

"At 12 a.m. there aren't too many officers riding around in their cars," said one officer. "When calls stack up all you can do is put them out for bids and pray."