University of California Transportation Center

Streets are more than public utilities, more than mere traffic conduits, more than the equivalent of water lines and sewers and electric cables, more than linear physical spaces that permit people and goods to get from here to here. To be sure, communication remains a major purpose, along with unfettered public access to property. These roles have received abundant attention, particularly in the latter half of the twentieth century. Other roles have not. 

Streets shape the form and comfort of urban communities. Their sizes and arrangements give or deny light and shade. THey may focus attention and activities on one or many centers, at the edges, along a line, or they may simply direct one's attention to nothing in particular. The three streets that lead from the Piazza del Popolo in Rome, Via del Corso in the center give focus to that city as does nothing else. So does Market Street in San Francisco and a hundred Main Streets in small cities across the United States.