Unprecedented Public Safety Plan for Obama Inauguration

Jan. 7, 2009— -- Virtually every major bridge heading into the nation's capital on Inauguration Day will be closed to vehicular traffic. In other words, unless they are on a bus or in an authorized vehicle, riders will be turned away by the police or the military.

That announcement came from the United States Secret Service, which is the organization tasked with handling security for the inauguration of Barack Obama as the 44th president of the United States.

The reasons for all the controls over traffic became clear Wednesday night as ABC News learned of a new security bulletin regarding the inauguration.

While there is no specific credible threat to the event, the government warning expressed concern about improvised bombs, suicide attacks and hostage scenarios. The reason? Intelligence officials have concluded that the inauguration is a very "attractive target" -- because of the symbolism, its historic nature, the presence of VIPs and the sheer volume of people expected in and around the ceremonies.

"There are no adjustments being made at this time to the nation's threat level," read the statement on the joint threat assessment by the Department of Homeland Security, the FBI, the National Counterterrorism Center, the National Geospatial Intelligence Agency, the U.S. Northern Command and fusion centers in the National Capital Region.

"As a routine matter, we also remind the public planning to attend the inauguration to be both thoughtful and vigilant of their surroundings, and to report anything suspicious to authorities," the statement added.

The most probable targets are thought to include crowds on the mall, hotels and restaurants and streets heading into the parade area.

All people along the parade route and at the balls will have to go through security screening. Some of the items restricted along the parade route beyond the obvious prohibition against weapons include aerosols, supports for signs and placards, packages, coolers, thermal or glass containers, backpacks, bags exceeding size restrictions (8" x 6" x 4"), laser pointers, animals other than helper/guide dogs, structures, bicycles and any other items determined to be a potential safety hazard.