The 25-mile-per-hour speed limit that went into effect in New York City on Friday did not slow a black Mercedes that blazed a path down the middle lane of Madison Avenue at a brisk 34 miles per hour around 1 p.m. Nor did it deter the drivers of a tow truck going 32 m.p.h. or a city bus lumbering along at 28 m.p.h. Even a police car was spotted darting through traffic, though no emergency was apparent.

In a city where any hint of open asphalt can take the edge off a day mired in traffic, the dawn of a new speed limit did not change much.

Cluttered roads still seemed to dictate speed far more than did the city’s new mandate, which dropped the default limit from 30 m.p.h. to 25.

Fear of enforcement was palpable. “Snitches get stitches!” one passer-by called out to a reporter who was monitoring cars’ speed with a radar gun on Madison Avenue near 39th Street.