Robert J. Ross, 25, just out of jail and sporting the beige and blue bathrobe he was wearing when he was arrested, stood outside the Prince George's County courthouse in Upper Marlboro one recent afternoon trying to find a way home. "This is as out of the way as you can get," he said.

"If you can't make a personal contact with a relative and don't have enough money, you get into a situation with loitering--and indecent exposure," said the Hyattsville man, who had been about to take a shower when police arrested him on a marijuana possession charge. He wrapped the robe tighter around his bare chest.

"People are looking at me like I'm crazy. It's a disgrace to the county and it's a disgrace to me to have to be waiting around, loitering," he said. "Why don't the people have a shuttle service?"

You can go by bus from the District to Rockville, Fairfax City, Baltimore, Buffalo and Baton Rouge. But there's no public transportation in and out of the county seat of the largest jurisdiction in the Washington Metropolitan Area.

County Sheriff James V. Aluisi Jr., himself a resident, says: "Transportation in Upper Marlboro? . . . It's non-existent . . . Marlboro is just a beautiful little town but there's no access to it."

Upper Marlboro, whose full-time population is a shade over 300, (and about 800 including prison inmates), is nestled in a valley in the tobacco-growing country just two miles from the Anne Arundel County line. To get there by Metrobus, you ride to the end of the line at Andrews Air Force Base and walk eight miles east on Route 4. By Metrorail, you surface at Addison Road, walk three miles out Central Avenue, then hike seven miles south on Landover Road, Rte. 202. Or you thumb a ride.

Most people visiting town can arrange rides with friends and relatives if they do not have a car, but criminal defendants and released inmates who arrive in police cars and paddy wagons often have trouble getting home.

Residents of the town sometimes complain of convicted felons and other undesirables roaming their backstreets at twilight.

Last fall, the complaints induced the sheriff's department to start carting released prisoners out of town in a paddy wagon. The service picks up its passengers behind the jail each night at six, and deposits them at the Addison Road metro station. But not everybody wants to go to Addison Road, and the paddy wagon attracts only one or two ex-prisoners a day.

The Rev. Robert McGuigan, assistant pastor of St. Mary's Catholic Church in Upper Marlboro, says that released inmates used to knock on his door looking for help getting home.

"There's no way of getting out of town, and they're nervous walking around," said McGuigan, who is also the Roman Catholic chaplain at the county jail.

"I just think, as a county seat, the public is entitled to some public transportation . . . As a county seat, we're practically inaccessible," he said.

A fellow named Thomas Raymond Smith Jr. hit the pavement just before sunset one day last week, his release papers in his pocket and his clothes tied up in the legs of a spare pair of jeans.

He had enough money for a bus, he said, but nowhere to spend it. He said fellow inmates had warned him: "If you don't know somebody, you're on your own. They don't have any services or anything for transportation to get home."

The county experimented with a bus service five years ago. For six months a bus plied every 30 minutes between Upper Marlboro and the Penn-Mar Shopping Center in Forestville. "There was one passenger on average--that's pretty low," said county transportation director Vaughan Barkdoll. "The hue and cry for the need is there, but the ridership isn't."

The county operates two radio-dispatched 12-passenger vans in the southern end of the county, and sometimes they drive between Upper Marlboro and Metrobus stops at Andrews.

But John Johnson, administrative assistant with the transportation department, says the service already is operating at full capacity with no money for expansion.

Joseph Gallagher, of the county public defender's office recalls one elderly client who was forced to hitchhike from Maryland's Eastern Shore with the aid of a walker, to attend a nonsupport hearing in Upper Marlboro and another who had to hitchhike with a walker from Southeast Washington.

"Hitchhiking with a walker is just ridiculous but that's what they had to do," he said.

Gallagher notes it isn't easy for someone to hitch a ride in and out of Upper Marlboro because "drivers aren't dumb" and realize many of the hitchhikers are criminals. "They know what they'd be picking up and they aren't going to take the risk," he said.

Not everybody complains, however. Last Tuesday evening, Bob Federline, a 48-year-old unemployed man with a brush haircut and a few days growth of beard who had been visiting friends in Upper Marlboro was walking home to 32nd Street in Mount Rainier. "I'm not looking for a ride--just planning to walk," he said.

"It's a pretty long road," he said, "but it's all right as long as there aren't too many cars on it. It's a pretty good walk--it's about 20 miles. Not too much traffic. Maybe if someone came out of the bushes and chased you, that would be the only problem."