Circulation

Rue Saint-Jacques, a street in Montreal, 1910

Circulation, or less broadly, transportation, is perhaps a street’s most visible use, and certainly among the most important. The unrestricted movement of people and goods within a city is essential to its commerce and vitality, and streets provide the physical space for this activity.

In the interest of order and efficiency, an effort may be made to segregate different types of traffic. This is usually done by carving a road through the middle for motorists, reserving sidewalks on either side for pedestrians; other arrangements allow for streetcars, trolleys, and even wastewater and rainfall runoff ditches (common in Japan and India). In the mid-20th century, as the automobile threatened to overwhelm city streets with pollution and ghastly accidents, many urban theorists came to see this segregation as not only helpful but necessary in order to maintain mobility. Le Corbusier perceived an ever-stricter segregation of traffic as an essential affirmation of social order--a desirable, and ultimately inevitable, expression of modernity. To this end, proposals were advanced to build “vertical streets” where road vehicles, pedestrians, and trains would each occupy their own levels. Such an arrangement, it was said, would allow for even denser development in the future. These plans were never implemented on a large scale, a fact which today’s urban theorists regard as fortunate for vitality and diversity.

Transportation is often misunderstood to be the defining characteristic, or even the sole purpose, of a street. This has never been the case, 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, or children at play. Many streets are bracketed by bollards or Jersey barriers so as to prevent passage unless on foot. 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.