The Manhattan White House of Donald J. Trump is in the center of one of the busiest and richest urban corridors in the world, close to major corporate and bank headquarters and expensive high-rises. The protection of Mr. Trump during visits to Trump Tower presents challenges unlike those of any previous president.

Mr. Trump lives in the three top floors of Trump Tower at Fifth Avenue and 56th Street, atop 38 floors of residences, 13 stories of commercial offices and seven floors of public retail space, all planted in a teeming office, residential and shopping district three blocks from Central Park.

In addition to whatever fortifications and personnel the Secret Service deploys but doesn’t talk about, the city has assigned 50 additional traffic agents and police officers to manage flow, and has posted surveillance officers on elevated platforms and rooftops. Bomb-sniffing dogs and plainclothes police officers patrol the vicinity, and heavy-weapons teams are nearby, according to the police chief of department, Carlos M. Gomez.

A glimpse of what New Yorkers will see as the transition continues:

The president-elect and residents of Trump Tower’s 263 apartments enter on 56th Street, and the sidewalk along the north side of 56th Street is closed from Fifth Avenue to Madison Avenue. The street itself is blocked at either end, with high-speed crash barriers that can be opened for delivery vehicles.

A second level of security applies to the sidewalks on the south side of 56th Street and the east side of Fifth Avenue, where as many as 25,000 pedestrians walk during rush hours. Bags are searched at checkpoints on the corners.

In addition, the two easternmost lanes of Fifth Avenue from 55th to 57th Streets have been closed. The others remain open except in emergencies or to accommodate protests. Thousands of cars and 140 city buses pass by the tower at rush hour, and Chief Gomez said the closing, in effect for the transition, might be reconsidered later.

The retail and commercial areas of the building can be entered from Fifth Avenue, and from a connecting building at 590 Madison Avenue, and security personnel there scan bags with X-ray equipment. Trump businesses use offices on the 26th floor, accessible from these entrances. The tower has an atrium with retail stores, most of which are empty, along with some rooftop gardens on the fourth and fifth floors that are supposed to be open to the public.