Inauguration-goers may be turned away from the inaugural parade route once crowds reach a certain capacity.
The area can hold about 300,000 to 350,000 spectators, Secret Service Director Mark Sullivan said. Everyone will be screened at checkpoints before entering the viewing area. Once capacity is reached, checkpoints will be closed and no one else can enter the area around the parade route.
That number does not include the 5,000 people who will be sitting on bleachers along the route.
"There's just a finite amount of people we can put on the parade route," a security official told the Washington Post. "For safety and fire reasons, we'll have to cut it off."
Maryland Gov. Martin O'Malley, Virginia Gov. Tim Kaine, D.C. Mayor Adrian Fenty and a Secret Service representative gathered Tuesday to emphasize that people heed road and bridge closures and restrictions and follow security guidelines.
Kaine defended the bridge closures from Virginia to D.C., saying that with restrictions in the city, keeping those bridges open would result in massive gridlock.
Fenty told people who plan to attend the swearing-in ceremony to forget about trying to get a spot along the parade route, which is expected to be packed well before the swearing-in is over. Security checkpoints surrounding the parade on Pennsylvania Avenue will open at 7 a.m. and the area likely will be filled within three hours, Fenty said. The parade is not scheduled to begin until 2:30 p.m.
Twenty Jumbotron screens will show the parade. Those screens also will be useful for those finding their movement through the area limited. There will be only two designated areas to cross Pennsylvania Avenue.
Fenty, Kaine and O'Malley also reminded inauguration-goers to be prepared to be outside for several hours.
Officials also noted that of the expected 10,000 charter buses expected to come to D.C., only 3,000 have been registered.