A street is the basic unit of urban space through which people experience a city. It is often misconceived as the two-dimensional surface that vehicles drive on when moving from one place to another. Streets are, in fact, multidimensional spaces consisting of many surfaces and structures. They stretch from one property line to another, including the building edges, land uses, and setbacks that define each side. They offer space for movement and access and facilitate a variety of uses and activities. Streets are dynamic spaces that adapt over time to support environmental sustainability, public health, economic activity, and cultural significance.
Streets are like outdoor rooms shaped by multiple planes: the ground plane at the bottom, the buildings and the roadbed edges as the side planes, and the canopy plane like the ceiling of the room. Each plane is constructed of many individual elements that are often regulated or created by a range of different policies, codes, guidelines, and building practices.
Understanding the various portions of a street as either continuous or interchangeable offers a flexible approach to street design. While sidewalk clear paths, bike lanes, and travel lanes must be continuous and connected in order to function effectively, interchangeable elements such as parking spaces, trees, parklets, and transit stops allow a street to be adapted to serve its context. The terms below broaden the definition of street.