November 11, 2014 9:42 AM EST

The difference between traveling 25 and 30 miles per hour may seem minute for the average car driver. The faster speed would save you about five minutes in a trip down the length of Manhattan. But the difference is profound if you’re hit by a car–maybe even the difference between life and death.

In effort to curb traffic fatalities, New York City lowered its default speed limit to 25 mph effective Nov. 7. It’s a move that, if properly enforced, experts say could inspire similar moves in other urban areas across the country—making a dent in the more than 4,000 pedestrians killed by cars each year in the U.S. “All eyes are on New York right now to see if we can tame our infamously mean streets,” says Paul Steely White, executive director of New York-based Transportation Alternatives.

The move is perhaps the biggest effort yet from Mayor Bill DeBlasio to reduce the number of traffic-related deaths in New York City. Hundreds of New Yorkers die annually in traffic accidents and, in recent years, a number of highly publicized deaths have inspired public relations campaigns. Most dramatically, DeBlasio recently introduced Vision Zero, a program designed to eliminate traffic fatalities altogether in New York.

The speed limit reduction plays a key role in Vision Zero, though no one expects the city to change overnight. Police first need to enforce the rule, something some city-dwellers think isn’t likely. But if it’s enforced, the lower speed limit could have profound effects. A car that hits a pedestrian while traveling 30 mph is twice as likely to kill that person as if it were traveling 25 mph. And it’s eight times as likely to kill a pedestrian than if it were traveling 20 mph, the average top speed that a sprinting human might collide into another object.

“The five-mile per hour difference makes a huge difference between life and death,” says White. “Moving forward, in terms of enforcement, it’s a question of whether we’ll save dozens of lives or scores or perhaps hundreds if we do enforce the speed limit.”

Slowing the roads may being about other unintended consequences, too. “What we’re trying to say is this is not just about changing speed, it’s about changing what goes on in people’s heads,” said John Whitelegg, a professor at the University of York who has helped implement programs to lower the speed limit in Germany and the United Kingdom. Whitelegg said that in the places he’s worked, researchers have found links between lower speed limits and increased physical activity. In turn, rates of obesity and diabetes are also down.

“There’s a tremendous value to being able to walk to work, walk to school,” White said. “Dare I say, that’s becoming the new American dream.”

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