Life In Rome, Italy

These plans were never implemented comprehensively, a fact which today's urban theorists regard as fortunate for vitality and diversity. Rather, vertical segregation is applied on a piecemeal basis, as in sewers, utility poles, depressed highways, elevated railways, common utility ducts, the extensive complex of underground malls surrounding Tokyo Station and the Ōtemachi subway station, the elevated pedestrian skyway networks of Minneapolis and Calgary, the underground cities of Atlanta and Montreal, and the multilevel streets in Chicago.
Transportation is often misunderstood to be the defining characteristic, or even the sole purpose, of a street. This has not been the case since the word "street" came to be limited to urban situations, and even in the automobile age, is still demonstrably false. A street may be temporarily blocked to all through traffic in order to secure the space for other uses, such as a street fair, a flea market, children at play, filming a movie, or construction work. Many streets are bracketed by bollards or Jersey barriers so as to keep out vehicles. These measures are often taken in a city's busiest areas, the "destination" districts, when the volume of activity outgrows the capacity of private passenger vehicles to support it. A feature universal to all streets is a human-scale design that gives its users the space and security to feel engaged in their surroundings, whatever through traffic may pass.