New Year arriving under tight security
Revelers wear orange hats in NY's Times Square
A heavily armed policeman looks on during the New Year's Eve party in New York's Times Square.
CNN's Jason Carroll on security for New Year's Eve.
The pros and cons of digital fingerprinting.
CNN's Alan Chernoff on Americans traveling despite the higher terror alert.
(CNN) -- Millions of revelers across the U.S. East Coast , including scores wearing orange hats in New York's Times Square, have ushered in the new year with laughter, tears, confetti and fireworks -- all closely monitored by unprecedented security.
The most expansive anti-terrorism efforts in U.S. history include airspace closures; elite teams trained to spot potential attackers from rooftops and helicopters; and thousands of police -- both uniformed and in plainclothes -- mingling with partygoers.
The U.S. military is aiding local law enforcement agencies as they respond to a recent rise in the U.S. terrorism alert level. The Homeland Security Department raised the level from yellow to orange, the second-highest rank on a five-tier scale, on December 21.
The department said intelligence chatter suggested terrorists may attempt attacks in the United States during the holiday period.
New York's Times Square is being monitored by helicopters and thousands of police officers. Visitors to the world's most televised celebration had to pass through magnetometers, or metal detectors, and have their bags searched in order to get to viewing areas.
New Jersey Gov. James McGreevey said authorities are concerned that emergency vehicles, such as ambulances, could be used in terrorist attacks. Hospitals have been asked to certify their vehicles so authorities can "monitor ambulances," particularly if they're heading to New York City, he said.
Police are conducting "random searches of all vehicles" entering the Lincoln Tunnel, McGreevey said.
And as a precautionary measure late Wednesday, all eastbound lanes of the George Washington Bridge -- going into New York City from New Jersey -- were closed. Electronic billboards had warned commuters since the start of the week that this closure would take place.
Authorities in Washington, D.C., began random checks of cars outside the Capitol Tuesday, but would not discuss other security measures for the nation's capital.
The city's deputy mayor, Margret Kellems, told CNN that despite increased security, people do not say they are frightened.
"I think the number of folks you see, particularly the tourists out in the street, are showing that people really are being very bold and they are being vigilant," Kellems said. "They are calling in when they're concerned about something, but the rest of the time they are out there enjoying themselves and not letting this get the best of them."
Las Vegas closes its skies for big show
The hotel-and-casino-filled Las Vegas Strip will have its annual fireworks display and the city's airspace will be closed for six hours, Nevada Gov. Kenny Guinn told CNN Wednesday. It's the first time the skies over Las Vegas are being brought to a "standstill," he said.
"With about 300-plus thousand people in less than a two-mile stretch in a very narrow area, we thought that was a prudent thing to do just to provide the ability for our well-organized team of first-line responders, metropolitan police, and other staff members that's been assigned," he told CNN.
The city "maximized" its law enforcement presence for the holiday and will have military helicopters flying overhead, he said. "I think we're just much more organized and being more prudent and vigilant. And we've asked all the people just to keep their eyes and ears open."
Although there are no specific threats against the city, "Las Vegas has been certainly mentioned in the chatter from the intelligence that we receive from Homeland Security in Washington, D.C., and they've had a special team here visiting with us," Guinn said. "We just want to make sure that we've done everything we can to promote safety, and have a good time."
West Coast being careful
In Los Angeles, police are on 12-hour shifts in many areas, the police department said. The FBI said federal agents will work along with local authorities at New Year's events in the area Wednesday night and Thursday, including the Rose Parade and Rose Bowl game in Pasadena.
"The key thing is we want people to be vigilant, but we also want people to enjoy the freedoms this country has given us," Los Angeles Mayor James Hahn said. "We want people to have a good time, a safe time tonight, have a happy new year, but we want to do the worrying for them."
There will be 1,000 police on hand over the next two days, the Pasadena Police Department said. Pasadena itself has 227 officers -- the others have come in from surrounding areas, the department said.
Airspace over the parade route and the Rose Bowl will be restricted to military and police aircraft, and people who come to the game or view the parade from grandstand seats should expect to be searched, the department said. Cars parked near the parade route will be subject to search as well, the department said.
Also, no umbrellas will be allowed into the stadium Thursday -- even if it's raining.
The city of Seattle is partying, but playing it safe.
Seattle canceled its millennium celebrations in 1999 after al Qaeda operative Ahmed Ressam tried to enter Washington state with explosives in the trunk of his car.
Ressam was later convicted of several charges, including conspiracy to commit an act of international terrorism. He was sentenced to 27 years in prison, a deal which cut his original sentence in half, provided he testify against accomplices.
Seattle Police Chief Gil Kerlikowski said police have taken "extraordinary steps" to increase security since 1999.
"We have a good plan in place [for New Year's Eve], people should come out and enjoy themselves," he said.
Checking for risky material
Chicago and St. Louis, Missouri, have stepped up checks of trucks to make sure they are not transporting hazardous materials, said Michael Chamness, chairman of the Illinois Terrorism Task Force.
Units trained to respond to an attack involving weapons of mass destruction or hazardous materials are at the ready, as are many medical response teams, he said.
Chicago police spokesman Pat Camden said security precautions at Navy Pier, the city's largest New Year's Eve celebration, include a stepped-up police presence.
Similar measures were taken last year, when the alert level was also at orange, he said. "What we're doing is what we've been doing," he said. "We've identified areas of concern where we'll have additional police."
Flight restrictions are also in effect in Chicago.
Security continues into New Year
Miami has also increased security in and around the Orange Bowl, set for New Year's Day. Police Chief John Timoney said the added measures are something people will learn to live with.
"Life has changed post-September 11," Timoney said. "It's something we'll have to get used to, but as much as possible, as much as humanly possible, people should resume normal activities, and particularly New Year's Eve."
At Disney World in Orlando, Florida, which holds popular fireworks displays at three of its four theme parks, the Orange County Sheriff Department is beefing up its presence, said Disney World spokeswoman Rena Langley.
She said Disney World does not discuss other security measures, because doing so could "compromise their effect."
"We are in constant contact with local, state, and federal law enforcement," she said.
In Atlanta, hundreds of additional police officers -- some working undercover -- were at major events, including the annual "peach drop," a version of New York's ball drop, said Atlanta police spokesman John Quigley.
Additional patrols are protecting infrastructure such as communications and electrical facilities, and police are coordinating with private security at "high-risk" locations such as CNN Center and Coca-Cola headquarters, Quigley said. Atlanta police are in "constant communication" with federal authorities.
CNN correspondents Jamie McIntyre, Charles Feldman and Kris Osborn, Los Angeles Assignment Editor Carey Bodenheimer and Producer Deanna Proeller contributed to this report.