More than 100 NYPD officers were already patrolling Broadway between 41st and 45th Streets at 9:30 this morning, conducting security checks for early arrivals at 44th Street and discarding backpacks in large plastic dumpsters as part of the most heavily-policed Times Square New Year's celebration in the city's history. By noon, the area was packed.

This year's security procedure is detailed for visitors on the Times Square Alliance Website, and will entail, for the first time, a minimum of two wand screenings per attendee—once when entering through one of 14 access points to the so-called "secure zone" and again at the entrance to "pens" where people will wait for the ball to drop.

Backpacks of any kind are prohibited, a standard measure that nevertheless took many early arrivals by surprise this morning. We saw at least one officer patiently helping a tourist go through his backpack, while another complained that there was no time for such focused attentions.

We did, however, see attendees passing through with snacks and blankets. Alcohol is, as always, prohibited.

Other tight security measures this year include the sealing of manhole covers from 41st Street to 50th Street along 6th-8th Avenues, radiation detectors throughout the area, plainclothes officers dispersed throughout the crowd, and officers stationed at rooftop posts. Several bomb-sniffing dogs were already on the square this morning.

Newspaper vending machines and trash cans will also be removed or locked on Broadway and Seventh Avenue from 34th to 59th streets, a counterterrorism tactic influenced by the 2013 Boston Marathon bombing when bombs were hidden in trash cans.

Attendees will be prohibited from passing back through security to use bathrooms today, prompting some to bring supplies.

At a press conference earlier this week, City officials said that there will be, at peak, about 6,000 police officers stationed on or near Times Square, about 600-800 more cops than New Year's Eve 2014. The city's 500-strong counterterrorism unit will be on patrol, in addition to 1,200 new recruits on their first assignment following graduation from the academy on Tuesday.

One million attendees are expected.

"The usual elements will include thousands of uniformed police officers in the subways, in the air and the waterways around New York City," Chief of Detectives James O'Neill told reporters.

"Five thousand officers assigned to Times Square, hundreds of traffic agents, plus additional mobile cameras, chemical and radiation detectors, specially-trained police dogs sniffing for traces of explosives, cops on horseback, helicopters and police boats," he added. "We will have observation posts manned by… officers looking for suspicious activity, while cops in plainclothes keep watch on the crowds."

Heightened security has been the norm in NYC in the aftermath of November's terrorist attacks in Paris that killed 129 people, even as Mayor de Blasio and NYPD Commissioner Bratton have urged New Yorkers to conduct their business as usual. Threats have been rumored and dismissed. Counterterrorism efforts have been tested and boasted about.

"We are not aware of any threat we deem credible," NYPD Commissioner William Bratton said in a statement about New Year's Eve. "We have a constant threat analysis stream that we are constantly reviewing. But again, we are not aware of any threat at this time we deem credible to this event in Times Square."

If you're hoping to avoid the mess altogether, here's a review of today's street closures.

Additional reporting by Jen Chung.