Expect chaos in Ann Arbor on Saturday.

Expect streets to be closed, either partially or entirely. Expect traffic jams. Expect areas where parking is normally available to be blocked off.

And expect security to be tight - really tight.

Barack Obama

"For us here in Ann Arbor who aren't used to it, this will be an unprecedented amount of security," said Mayor John Hieftje. "We haven't had a sitting president in town for some time."

Barack Obama will be the first sitting president in Ann Arbor since George H.W. Bush was here in 1991. Obama arrives Saturday to deliver a commencement address to a crowd of 80,000 at Michigan Stadium.

And with a presidential visit comes a unique set of logistical challenges.

The U.S. Secret Service has been in town this week, talking with Police Chief Barnett Jones and other law enforcement officials from the University of Michigan and Michigan State Police to work out a game plan. Naturally, the details remain confidential.

Hieftje has some advice, though.

"If you're going, get there early, and don't expect to be able to drive through that section of town any more quickly than you would on football Saturday," he said.

Michigan Stadium gates will open at 6:30 a.m. Guests are urged to arrive no later than 9 a.m. The ceremony begins at 11 a.m.

The university has made efforts to put almost all of the information anyone needs to know about commencement day on its website. The site includes detailed maps of commencement activity locations, parking, shuttles and more.

University officials say the enhanced security means several roads and parking lots near the stadium won't be available for use. In addition, the number of graduates participating this year has increased dramatically, so there will be even more congestion than normal.

Jim Kosteva, a U-M spokesman, said the university is establishing a secure area around Michigan Stadium - bordered by Stadium Boulevard to the south, Hoover Avenue to the north, Main Street to the west and the railroad tracks to the east.

"We're certainly used to being able to conduct the major events in and around the Big House and we're certainly used to accommodating large crowds," he said. "This sort of combines all those unique elements into one. So I would say there's a very good, well-organized team in place that's working with the federal officials and working through our staff and working in cooperation with city police as it relates to security."

The City Council last week approved a plan to close streets and placed limitations on activities during commencement. Existing peddler/solicitor permits and sidewalk occupancy permits will not be valid in areas around the stadium.

University Planner Susan Gott said the following street closures will be in effect from midnight Friday to 2 p.m. Saturday:

â€¢ Kipke Drive — closed to all vehicles and pedestrians. â€¢ South Main Street — closed to all vehicles (between Pauline Boulevard and East Stadium Boulevard), open for pedestrians. â€¢ Keech Avenue — restricted vehicle access (between South Main Street and Greene Street) for shuttle bus traffic, open for pedestrians. â€¢ Greene Street — restricted vehicle access (between Hoover Avenue and Keech Avenue) for shuttle bus traffic, open for pedestrians. â€¢ East Stadium Boulevard — restricted vehicle access on one lane of westbound East Stadium Boulevard (from Stadium Way to South Main Street) for shuttle bus traffic, open for pedestrians.

Traffic will be detoured around the South Main Street section closure onto Pauline Boulevard, South Seventh Street and Scio Church Road. Signage will be posted directing drivers.

Due to increased security, some lots that are closer to the stadium are closed or are for restricted parking only. These include: SC2, SC3, SC4, SC5, SC6, SC7, SC11, SC32, SC35, SC38 and SC41.

All vehicles must be removed from those lots by Friday at midnight or they will be towed. Most other parking lots and structures will be open to serve commencement guests on Saturday.

Normal U-M bus service will be limited to the spring/summer Northwood route.

This map shows parking areas that will be restricted on Saturday.

Drivers are urged to plan routes with alternatives in mind. If traffic is re-routed to accommodate the arrival of the president’s motorcade —Â which likely will happen sometime after 9 a.m. — police will instruct drivers on alternative routes.

Residents living in the vicinity of the stadium will be afforded game-day parking privileges on Saturday, meaning vehicles can park in any legally marked on-street space as well as private lawns and driveways. However, there may be pedestrian or parking restrictions imposed near the stadium.

"There's going to be a real shortage of parking in and around the stadium," Kosteva said. "But we are planning to implement a very aggressive set of shuttles coordinating and working from most all the area hotels as well as a number of different locations and parking structures on the Central Campus."

University officials expect a crowd of about 80,000 inside the Big House. Nearly 60,000 of those seats are reserved for graduates and their families.

Leftover tickets will be available to other U-M students, faculty and staff starting today. Anyone with a university ID can request up to two tickets. If there are additional tickets, they will be available to the general public starting at 9 a.m. Friday at the ticket office in the basement of the Michigan Union.

The commencement address will be broadcast live on the Big Ten Network and streamed live on the web starting at 10:30 a.m.

Ryan J. Stanton covers government for AnnArbor.com. Reach him at ryanstanton@annarbor.com or 734-623-2529.