The speed limit on an eight-mile stretch of Atlantic Avenue and two dozen other major roadways is being cut from 30 to 25 mph as part of Mayor Bill de Blasio's Vision Zero initiative to reduce pedestrian deaths.
The New York City Police Department will also be launching stepped-up enforcement citywide.
"Today, we're launching what is going to be the first in a series of 25 arterial slow zones," said Polly Trottenberg, commissioner of the New York City Department of Transportation. "We're beginning here on Atlantic Ave. We're going to go all the way from the river down in Brooklyn Heights to Woodhaven in Queens."
"We can have free-flowing arteries without having senseless blood from traffic-related speed accidents," said Brooklyn Borough President Eric Adams.
The Grand Concourse and Queens Boulevard are among the 24 other roads targeted by Vision Zero.