Craning over his shoulder, Douglas Tully slowly, cautiously maneuvered his 60-foot delivery truck down a block of West 56th Street in Midtown Manhattan — in reverse.

“I’ve seen a lot of things as a truck driver, but this has got to be a first, ” said Mr. Tully, 40, who had delivered a rug near Trump Tower only to find he could not exit the one-way street; 56th Street was blocked off at Fifth Avenue by the police, blast barricades and bomb-sniffing dogs. As vehicles nosed toward Fifth Avenue, officers stopped each one, forcing them back down the street against traffic.

Ever since Donald J. Trump was elected president last month, the sidewalks around his black-glass home and office on Fifth Avenue have been clogged with gawkers, security barriers and officers who search shopping bags filled with presents.