Functional classification is an ordering system that defines “the part that any particular road or street should play in serving the flow of trips through a highway network.” Functional classification categorizes streets according to their ability to 1) move traffic, and 2) provide access to adjacent properties. Street types under functional classification include “local streets,” medium-sized “collectors,” and highway-type “arterials.”
Many city streets predated the advent of the Federal Highway System of functional classification, making the system unsuitable for the diversity of land uses and travel characteristics throughout an urban area. While certain types of classification make streets eligible for highway aid, once a street is given a class, federal design standards that do not consider local context may be assigned to that street, and any variation requires a design exception.
Classification schemes in and of themselves are rarely adequate as a design tool for the diversity of situations to be encountered on city streets.
Many cities have developed street classification systems specific to Avenue their local needs. These classification systems generally combine 2–3 variables that guide decision-making:
In December 2010, San Francisco’s Board of Supervisors adopted a new, comprehensive street design guidebook including developer requirements entitled the Better Streets Plan. Numerous city codes were changed to facilitate implementation of the adopted guidelines on city streets—any changes to the right-of-way must follow the new standards. These include necessary sidewalk width, street trees, and intersection design templates. The design guidance all corresponds to a series of street typologies that factor together street type and land use context.
Adapted from the Urban Street Design Guide, published by Island Press.