Checkpoints around Manhattan made for a tough day, but one would hope a safer day as police checked countless vehicles even into the night.
Pulled over at random, trucks of all sizes are being searched and even drivers in their cars are having their licenses checked.
The checkpoints are designed to squeeze down the traffic into one or two lanes. Officers can then scan each vehicle, and then select the ones they want to stop and search.
The down side to these security checks was massive traffic jams. Authorities stopped vehicles at the 59th Street bridge, which connects Manhattan to Queens, causing a major backup. The Brooklyn Bridge was down to one lane, and checkpoints were up near Times Square and in other Midtown locations.
As pedestrians watched, they were left to wonder if they feel safer.
"I guess. Everyone has to be careful to what's going on," said one person.
"We all have to take precautions and to be careful," another one said.
To make sure the bridges and tunnels are safe too, Port Authority officers are randomly stopping trucks on the George Washington Bridge.
Drivers are being asked to open their cargo bay so that it can be inspected.
Officers too were on high alert at tunnels checking some vehicles with radiation detectors.
On Friday morning, the mayor rode the subway down to City Hall to try to assure commuters the city was prepared.
"We don't want al-Qaida or any other organization ... to take away the freedoms without firing a shot," Mayor Michael Bloomberg said after getting off the train near the Brooklyn Bridge. Bloomberg urged New Yorkers to just "go back to work. And leave it to the professionals."
Police planned a show of force at Grand Central Terminal, Pennsylvania Station and the Times Square subway station because of a previously planned counterterror drill with rail agencies.
Security worker Eric Martinez wore a pin depicting the twin towers on his lapel as he headed to work in lower Manhattan on Friday, unfazed the unconfirmed terror threat.
He worked downtown then and lived through it. He still works there - and didn't hesitate to take the subway.
"It's the only way you can get to work. If something's going to happen it's going to happen. You just have to deal with it," he said. "This is the time we live in. If you're going to be afraid, you're just going to stay home."
At Penn Station, transit police in helmets and bulletproof vests and carrying assault rifles watched the crowds.
Officials were swabbing passengers' bags near an escalator to the train platforms, and police searched the bags of passengers at the entrance to a subway station. National Guard troops in camouflaged fatigues moved among the throng, eyeing packages.
Roseanne Lee, 64, said her taxi was stopped twice at police checkpoints on its way from the Upper East Side to Penn Station. Police looked in the windows of the cab but did not question her or the driver, she said. At one checkpoint, police were searching a moving van, she said.
The delays made the fare higher, "but I don't care," Lee said. "It's better to be safe. You can't stop doing what you're doing because of these threats. You just have to be careful."
Gail Murray, an administrative assistant who works in Manhattan, took the threat in stride as she listened to Long Island Rail Road announcements aboard a train heading to Penn Station.
"I thought, `Here we go again,"' she said. "That's all just part of living in New York City."
The measures were nothing New Yorkers - or the well-prepared law enforcement agencies - haven't seen before, Bloomberg said Friday.
"Keep in mind, we have threats all the time," he said on his weekly radio appearance on WOR. "On the Internet, every day, there are threats of people, particularly around big sporting events and religious holidays, and around commemorations of things like 9/11. And each time the NYPD, with the FBI, we increase our security, which obviously we have done for this."
City officials said there much would be done behind the scenes, in places that New Yorkers wouldn't even notice.
Bloomberg and Police Commissioner Kelly stressed the most important thing to do was to go on with life as usual.
Many New Yorkers were doing just that. Dressed in jeans and a Teamsters T-shirt, Michael Murphy of Seaford, didn't have terror threats on his mind as he headed to work at the armory at 26th and Lexington Avenue, where he was helping to stage shows for Fashion Week.
"Like they said last night, we have the greatest police department in the world," said Murray, 49. "I'm confident they'll do the job."
(The Associated Press contributed to this report.)