Owners of multimillion-dollar mansions are charging $30 to park on their manicured front lawns. The private Norwood School has become a taxi stand, and two-lane roads are bulging with charter buses barely able to squeeze between the painted lines.

As the U.S. Open kicks off Thursday at Congressional Country Club, one of Montgomery County’s most affluent addresses is expected to absorb 250,000 golf fans, workers and volunteers over the course of a week that began with practice rounds Monday.

Montgomery police and 20 state and federal agencies have spent the past year planning how to prevent a traffic meltdown during one of the largest single events ever hosted in the county. To forestall gridlock in the country-chic environs of Potomac and outer Bethesda, they have urged tournament goers to use 15,000 free parking spaces in satellite lots in Gaithersburg and at Dulles International Airport, where they can catch one of 450 shuttle buses to the tournament.

The Washington area is no stranger to major events, but they are usually closer to major highways and transit lines.

“I had to go around the Beltway and up I-270” to park, said a frustrated Pat Pericak of Arlington County as he headed to a shuttle bus Tuesday at the Montgomery County Fairgrounds. “I drove 20 minutes past the course. This is ludicrous.”

Congressional hosted the U.S. Open in 1964 and 1997, and it and the nearby TPC Potomac at Avenel Farm have held lower-profile professional golf tournaments since. But this is the first time the Washington region has hosted the U.S. golf championship in the aftermath of the Sept. 11, 2001, terrorist attacks.

County spokeswoman Lucille Baur said Montgomery police have coordinated security with state and federal authorities to protect 156 golfers, journalists from 42 countries, and thousands of spectators, including a slew of dignitaries expected in the stands. A golf tournament is especially challenging for police, Baur said, because security needs shift as the crowd follows players around the course.

Security is also tight to keep out a lengthy list of items. The most common contraband: cellphones, cameras, water and food. Bag checks and metal detectors are located at tournament entrances and before boarding shuttle buses at satellite parking lots.

Although cellphone bans are common at professional golf tournaments — no salsa music ring tones to pierce the hush of a backswing — some spectators were aghast that it was enforced so strictly.

“The PGA golf snobs won’t even let us have our cellphones on practice day?” one woman in a floppy hat huffed as she returned to her car Tuesday before boarding a shuttle bus at the fairgrounds parking lot.

Reg Jones, managing director of the U.S. championship, said cellphones have never been allowed at the U.S. Open, including during practice rounds.

Satellite parking 14 and 20 miles away didn’t sit well with some spectators, but others said they have come to expect parking-lot treks at major events.

“If [parking is] close, it’s expensive, so the 20- or 30-minute ride from here is no problem,” Pedro Perez of Waco, Tex., said as he and a friend returned to the fairgrounds Tuesday. “Free is a good price.”

A U.S. Golf Association spokesman said providing ample free parking from a few easily identifiable locations was the goal. The association wanted to streamline shuttle bus service and allow the buses at least two routes to the tournament.

“Just be patient with us,” Jones said. “The experience will be one [spectators will] always remember when they get here.”

To keep traffic moving, county officials have instructed homeowners selling parking on their lawns to haggle in their driveways, not in the road. The county Department of Permitting Services issued 15 parking permits to homeowners who paid $297 each.

Six zoning inspectors and investigators will be out daily through Sunday, said David Niblock, a specialist with the permitting department. Anyone caught charging for parking without a permit will be warned to stop and could be fined $500 if caught again, he said.

The topic of lawn parking is a tad touchy in Potomac. Some newbie parking attendants declined to talk. Others asked that their names not be published, as if there’s something unseemly about opening the locked iron gates and sitting in a lawn chair next to a big arrow on a hand-painted “Park” sign.

“It’s not considered cool,” one woman said in a hushed tone while glancing nervously from her circular driveway surrounded by parked cars.

“People think we’re exploiting the situation,” a man with her added.

One man accompanied by a German shepherd and collecting $30 from motorists in the long driveway of a stately River Road home gave a cool, “I’ve been instructed not to talk to the media.” Another man at a Bradley Boulevard home with columns was quick to say that the doctor who owns the house plans to donate his profits to a charity. A Norwood School administrator said the parking proceeds — spaces in the campus’s lot have been reserved by students’ families for up to $150 apiece — will go toward student financial aid.

Niblock warned that drivers should be especially wary of rain; that attractive parking spot on a lush lawn could turn to mud.

“I’ve seen Lexuses and Mercedes axle-deep in people’s front yards,” he said.