Someone asked Merrill Stabile, president of the city's largest parking company, where he should park tomorrow and Friday during the G-20 economic summit.

"I said, 'Your own driveway,' " Mr. Stabile joked.

Those bold enough to venture beyond their driveways during the summit will face a welter of restrictions and challenges, including a sealed-off Downtown, limited fringe parking options and wholesale detours in public transportation.

And while the city in general is opening its arms to the world, many businesses, schools, government offices and other enterprises will be closed.

So widespread were the planned closings of banks, restaurants and shops that one business, Prestogeorge Coffee Roasting Co. on Penn Avenue in the Strip District, posted an "Open for G-20" sign.

Michael Edwards, president and CEO of the Pittsburgh Downtown Partnership, said that nearly 100 eateries and 40 stores, including Saks Fifth Avenue, Macy's and Office Depot, would remain open.

"Some restaurants are even offering special G-20 menus ... If you're in town, there will be plenty of options to shop and eat," he said yesterday.

Patience and comfortable walking shoes will be a must for anyone hoping to reach the Golden Triangle during the summit.

Downtown will be off limits to most traffic from 12:01 a.m. tomorrow through Friday evening. Twenty-seven ramps and streets leading to the Golden Triangle will be closed.

Only one exit route -- the ramp leading down from Stanwix Street to the Parkway East's approach to the Fort Pitt Bridge -- will be closed.

The three motorist entry points -- Smithfield Street Bridge at West Carson Street, Fifth Avenue at Ross Street and Roberto Clemente Bridge at Isabella Street -- will be open only to vehicles of Downtown residents; buses, taxis and ACCESS vehicles; and certain delivery trucks.

The Fort Pitt and Fort Duquesne bridges will remain open, but exit ramps to Downtown will be closed. Temporary rolling closures of the Parkway West from Pittsburgh International Airport to Downtown to accommodate motorcades are possible today through Friday.

President Obama is scheduled to arrive aboard Air Force One at 3:30 p.m. tomorrow and depart shortly after 6 p.m. Friday.

Several streets in Oakland will be closed from 9 a.m. to midnight tomorrow for the evening's heads-of-state dinner at Phipps Conservatory and Botanical Gardens.

Protests might further disrupt travel.

The Pittsburgh G-20 Resistance Project is staging what it calls a "mass march" starting at 2:30 p.m. tomorrow at Arsenal Park, 40th Street and Penn Avenue, Lawrenceville.

The protesters intend to march to the summit site Downtown and have not obtained a permit. According to the group's Web site, marchers will engage in "diverse forms of resistance."

The march is "intended to allow people the space and freedom to oppose the G-20 how they see fit," the site says.

Mr. Stabile, president of Alco Parking, might make his living from cars, but for the summit he is recommending that commuters take the bus.

"My guess is that if you take the bus, you'll probably get here faster than if you drive," he said.

Not only is Downtown closed off, but two popular fringe options for parking are problematic.

The North Shore commuter lots will be closed until 9:30 a.m. tomorrow because the Pirates play an afternoon game at PNC Park. Those parking after 9:30 will be charged event rates of $10 and up.

Shuttles that typically operate from the North Shore to Downtown will be out of service tomorrow and Friday. Also, the Fort Duquesne Bridge walkway has been closed.

Commuter lots in the Strip District will be open, but the Secret Service security perimeter around the David L. Lawrence Convention Center will prevent anyone without credentials from walking directly into Downtown. Instead, patrons of those lots must take a bus to the North Side and from there either walk or catch a second bus into Downtown, Mr. Stabile said.

Better fringe parking options are the city's Second Avenue lot, Mellon Arena and Chatham Center, all of which are outside the restricted traffic zone.

Port Authority will operate service Downtown, but most buses will be detoured because of the summit's security restrictions. Light Rail Transit service will go only to First Avenue, with other Downtown stations closed.

Spokesman Jim Ritchie said the authority will try to adhere as closely as possible to its regular weekday schedules. "We know there is a possibility of events occurring that are out of our control that would slow service," he said.

He recommended that riders allow extra time to reach appointments and use the resources on the authority's G-20 Web site at portauthority.org/g20, which include route-by-route listings and maps of where buses will operate Downtown.