On Monday, New York City Mayor Michael Bloomberg unveiled a new event called “Summer Streets.” For three Saturdays in August, pedestrians and cyclists will enjoy exclusive access to a contiguous stretch of city thoroughfares running from the Brooklyn Bridge to 72nd Street. No cars allowed.

This goes way beyond street fair territory. We’re talking about a path more than half the length of Manhattan — 6.9 miles, to be precise — where people can walk, bike, shop, and otherwise enjoy the city free from the intrusion of motor vehicles.

The core idea behind Summer Streets, according to Transportation Commissioner Janette Sadik-Khan, is to change the way people view the city. “We’re really committed to treating our 6,000 miles of streets as more than just travel corridors, but as really vital public places,” she said at the Monday press conference. “For many of us, our streets are really our front yards and this new initiative will allow us to enjoy them free of vehicles.”

Or, in Bloomberg’s words, “It says to people, there’s other ways to get around.” By giving hundreds of thousands of New Yorkers (and tourists) a taste of urban streets with fewer cars, the thinking goes, public support will grow for building the infrastructure that alternative modes of transportation depend on.

This has been borne out in other cities. In Paris, the temporary conversion of an expressway by the Seine into a hugely popular public beach, known as Paris Plage, preceded the launch of the city’s bike-share system, Vélib, and other traffic-busting innovations. In Bogotá, an enormous car-free event called Ciclovía (“bikeway”) was accompanied by major improvements to the city’s pedestrian, bicycle, and transit networks. And in London, plans to pedestrianize Trafalgar Square served as a prelude to the implementation of congestion pricing.

While plans for congestion pricing in New York have suffered setbacks, the launch of Summer Streets may help shore up public support when the idea resurfaces. It also figures to strengthen the hand of advocates fighting for a safer, expanded bike network. Perhaps the most encouraging news is that Summer Streets is part of a trend: El Paso staged its variation on Ciclovía last summer, and other American cities — including Chicago, Philadelphia, Baltimore, Cleveland, and Portland — are also preparing major car-free events, setting the stage for policies to reduce car dependence.