President-elect Barack Obama's inaugural committee has pledged to make his Jan. 20 swearing-in ceremony the most "accessible" in U.S. history. But growing security concerns and staggering crowd estimates may be dissuading would-be witnesses from making the trip to Washington to be part of the historic event.

The Pennsylvania-based Red Lion Bus Company has canceled nearly all of its trips to Washington on inaugural week because passengers are steadily backing out of their reservations, the company's owner told

"Most passengers are canceling because they're not able to get tickets to any place where you could really see anything," said company owner Dennis Warner. 

And Red Lion's passengers might not be the only ones second-guessing their travel plans. 

Shortly after Obama's victory on Nov. 4, Washington Mayor Adrian Fenty said he estimated that 4 to 5 million people would attend the inauguration. City officials have reduced that number to 2 million, because it is impossible for the trains and local roads to enable 5 million spectators to reach the parade route or the ceremony at the Capitol.

"Accessibility is a big question right now," said Rebecca Pawlowski, director of communications for Washington's official tourism bureau.

"We're reminding people that the city has a lot of experience in handling big events -- it's something that happens here all the time -- but that said, this is an unprecedented crowd that's expected, so that requires a lot of patience, resilience and flexibility on the part of travelers and visitors," she said.

Obama's inaugural crowd estimates are indeed extraordinary. Lyndon B. Johnson's 1965 inauguration drew a record crowd of 1.2 million. Four years earlier, John F. Kennedy's inauguration -- blanketed in snow -- attracted approximately 1 million.

Pawlowski said the tourism bureau has received a bevy of phone calls from hopeful spectators expressing concern over everything from bathroom accessibility to weather to public transportation.

"We're advising people to do advanced planning," Pawlowski said.  "Metro (the commuter rail system) is expecting unprecedented crowds, so we're encouraging people to purchase Metro tickets in advance." 

The difficulty in finding a hotel room and the expense of paying for one if you do has also raised concerns among travelers.

Gail Esguerra, a guest services manager with the Grand Hyatt Hotel in downtown Washington, said the Hyatt was "flooded with phone calls" immediately after Election Day. Now, she said, the hotel's 888 rooms are sold out from Jan. 16 to the 25. 

Esguerra added that the Hyatt requires a minimum 4-night stay during the inauguration period -- a requirement that most hotels in the city have instituted -- and a costly one for many out-of-towners.

Some area residents, like Kevin Talley, are hoping to cash in on the hotel frenzy by advertising their apartments for rent on Craigslist.

Talley, a 29-year-old musician who lives approximately seven blocks from the White House, is asking $3,000 for four nights -- an offer he described as "pretty cheap." He said he has gotten several phone calls but no takers, even after he lowered his price from $5,000.

Even private party hosts have scaled back. MTV reportedly gave up its location in the vaunted Reagan Building for its unofficial inaugural ball.

Heightened security measures and warnings may also discourage would-be spectators from attending the inauguration. 

On Wednesday, the U.S. Secret Service, which is overseeing inauguration security, announced that all four major bridge crossings from northern Virginia into Washington will be closed -- except for bus and pedestrian traffic on the day Obama takes the oath of office.

A map released by the Secret Service shows about 3.5 square miles of downtown Washington closed to traffic starting midafternoon on Jan. 19, the day before the inauguration.

Streets will remain closed to most traffic until morning rush hour on Jan. 21, Obama's first full day as president.

The Presidential Inaugural Committee has also announced that baby carriages, backpacks and other large bags will be prohibited within all ticketed areas.  

The West Front of the Capitol is entirely outdoors, and there will be no tents or other covered areas in inclement weather. The only restrooms are porta-potties, and there will be no refreshment stands, the committee said.  

Asked whether the obstacles facing spectators might scale back their enthusiasm -- compelling them to watch the inauguration on television instead -- Pawlowski said, "It's hard to say. There are so many factors at play. Until the day of, it's really difficult to know." 

But Linda Douglass -- chief spokeswoman for the Presidential Inaugural Committee -- said major efforts are under way to ensure "greater accessibility" for those making the trip.

Douglass said a number of events -- including a children's concert, youth ball and neighborhood ball -- will be held free of charge or at reduced fares to maximize the number of attendees. Douglass said the committee has not decided how to distribute parade tickets yet.

"It's not going to be easy to get into D.C. by car, but what we have done for our part is to allow people to view it from a vantage point near the Capitol for free," she said. 

"We will be providing jumbo screens along the National Mall for free without tickets, which has not been done before. That was a key step to making sure more Americans who come to Washington can witness the swearing in." 

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The Associated Press contributed to this report.