Green Streets

One principle of green infrastructure involves reducing and treating stormwater close to its source. Urban transportation right-of-ways integrated with green techniques are often called “green streets”. Green Streets achieve multiple benefits, such as improved water quality and more livable communities, through the integration of stormwater treatment techniques which use natural processes and landscaping. Green streets can incorporate a wide variety of design elements. Although the design and appearance of green streets will vary, the functional goals are the same: provide source control of stormwater, limit its transport and pollutant conveyance to the collection system, and provide environmentally enhanced roads.

Street Trees and Curb Bulb Outs with Bioretention (Source: Low Impact Development Center)

Green Street Concept (Source: Low Impact Development Center)

Green Streets are designed to:

Mimic local hydrology prior to development
Provide multiple benefits along the street right of way including:

Integrated system of stormwater management within the right of way
Volume reductions in stormwater which reduce the volume of water discharged via pipe into receiving streams, rivers and larger bodies of water
Key linking component in community efforts to develop local green infrastructure networks
Aesthetic enhancement of the transit right of way
Improves local air quality by providing interception of airborne particulates and shade for cooling
Enhanced economic development along the transit corridor
Improved pedestrian experience along the street right of way.

Numerous approaches are available for creating Green Streets including:

Alternative Street Designs (Narrower Street Widths)
Swales
Bioretention Curb Extensions and Sidewalk Planters
Permeable Pavement
Sidewalk Trees and Tree Boxes

Here's information on Portland, Oregon's green streets program and green streets photos from the Low Impact Development Center.

Information is also available regarding several green streets projects, including a "green street" in Tacoma, Washington, the Growing Vine Street project in Seattle, Washington and the Baker Beach Green Street project in San Francisco. There are several more green infrastructure projects underway in San Francisco.

Here is a video Green Streets: The Road to Clean Water from U.S. EPA.