PHILADELPHIA — The motorcade carrying Lisa Monaco, the No. 2 law enforcement official in the United States, maneuvered between potholes and people on Kensington Avenue when her driver braked for a man wandering into traffic with a hypodermic needle dangling from his arm.

It was late June, and Monaco was in the city to address a particularly savage surge in drug abuse and violent crime here, shuttling to meetings with federal prosecutors, state and local police officials, and community members aimed at combating an annual spike in summer violence ushered in by the Fourth of July weekend.

“People are living in an environment they shouldn’t have to endure,” she said a few days later, recalling the drive from downtown to meet with beat cops in Northeast Philadelphia. “You actually have to step over needles to take your kid to the bus stop.”