“They’re pretty immovable,” he said.

And that is the point, the police commissioner, James P. O’Neill, said at a news conference on Thursday in Times Square with Mayor Bill de Blasio. While there are no specific threats related to the event, he said, the sand-filled trucks serve as a deterrent to the type of truck attacks in France and Germany that killed dozens of people and injured hundreds more.

President-elect Donald J. Trump, who has been at his estate in Florida, is not expected to be in Manhattan for New Year’s Eve, but the Police Department said Thursday that it expected close to two million people to converge on Times Square on Saturday for the annual ball drop.

“We’re going to have one of the most well-policed, best protected events at one of the safest venues in the entire world, given all the assets that we’ve employed here,” Mr. O’Neill said. “And all of this will ensure that New York City has yet another safe and enjoyable New Year’s Eve celebration, as we do every year.”

Sixty-five of the Sanitation Department trucks are part of a security plan that involves close to 7,000 police officers, assigned to guard against crime and terror by land, sea and air, as well as in the subway.

Beyond Times Square, some of the sanitation trucks will be stationed near a planned fireworks display in Central Park. Similar blockades will be put in place on the streets leading to the Coney Island Boardwalk as well as on the promenade itself. More than 100 police vehicles will also be positioned to restrict access to event sites.