Professional Practice

Transportation: Street

Streets are the stages on which we live our public lives. We use them to commute to work, run errands, exercise, and socialize. They are a defining element in the landscape, especially in cities, where streets represent roughly 30-35 percent of total land use. With smart design, we can create streets that encourage active and environmentally-friendly transportation options, respond to their context, foster equity and resilience, and provide ecosystem services.

The design of our streets influences how people travel. To encourage low-emission modes of transportation, streets should have ample room and dedicated lanes for pedestrians, cyclists, and mass transportation such as buses, streetcars, and bike share. Multi-modal streets move more people with fewer vehicles, and therefore result in lower emissions than conventional, automotive-centered street design.

Safe, dedicated, protected, and aesthetically-pleasing sidewalks and bike lanes do the same for walking and cycling, encouraging these healthy and more energy-efficient transportation modes. Wide sidewalks that exceed Americans with Disabilities Act (ADA) minimums create opportunities for pedestrian interaction and a more dynamic and robust public street life.

Bicycle lanes and sidewalks should be physically separated from vehicle traffic by trees, bollards, buffers, parked cars, or curbs wherever possible. Research has shown that physically-separated bike lanes yield the greatest safety gains for cyclists and, as a highly-visible piece of infrastructure, even have the potential to attract new cyclists. Vegetated buffers can further protect cyclists from harmful air pollution and should be incorporated whenever possible.

Green infrastructure should be widely used. Bioswales, rain gardens, and permeable pavement can be used to manage stormwater runoff and reduce flooding as well as create more aesthetically-pleasing streets. New construction should incorporate as many green streets features as possible, and existing infrastructure should be retrofitted to include green infrastructure. In Edmonston, Maryland, a 2/3 mile stretch of road was retrofitted with bioretention systems that now capture 90 percent of the first 1.33 inches of water on-site, helping to mitigate flooding and improve local water quality.

If planted with native, pollinator-friendly flowering species, green infrastructure can also serve an ecological function, providing forage and habitat for local wildlife and threatened pollinator species and supporting biodiversity.

Trees are the ultimate green infrastructure – they provide shade, reduce the urban heat island effect, capture rainwater, offer habitat for wildlife, enhance aesthetic and scenic values, and even improve public health. Diverse, regionally appropriate native tree species should be planted wherever possible in wide, spacious tree pits that provide ample room for the trees’ roots to grow. 


National Complete Streets Coalition



Beyond Complete Streets, The Dirt blog, October 18, 2016

Cool Pavements, Reducing Urban Heat Islands: Compendium of Strategies, U.S. Environmental Protection Agency

Creating Pollinator Habitats Along Roadsides, The Field blog, June 8, 2017

Designing Ecologically Sensitive Green Infrastructure that Serves People and Nature, The Nature of Cities, September 28, 2016

Green Streets Cut Pollution More Than Previously Thought, The Dirt blog, August 15, 2012

Green Streets Program, Philadelphia Water Department

Green Streets Program, Bureau of Environmental Services, City of Portland Government

Interview with Sandra James, International ASLA, City and Greenways Planner, City of Vancouver, ASLA

NACTO Urban Street Design Guide, National Association of City Transportation Officials, 2013

NACTO Urban Street Stormwater Guide, National Association of City Transportation Officials, 2017

NYC Street Design Manual, Department of Transportation, New York City

Reimagining Our Streets as Places: From Transit Routes to Community Roots, Project for Public Spaces

Stormwater Infrastructure & Streetscapes, Nathan Polanski, PE, for The Field blog, February 11, 2014


Demonstrating the Benefits of Green Streets for Active Aging: Final Report to EPA, Center for Transportation Studies and Institue on Aging, Portland State University, 2010

Lessons from the Green Lanes: Evaluating Protected Bike Lanes in the U.S., Transportation Research and Education Center, Portland State University, 2014

Rethinking Streets: An Evidence Based Guide to 25 Complete Street Transformations, University of Oregon Sustainable Cities Initiative, 2014 

Street-scale Green Infrastructure and Phyiscal Activity, EPA EnviroAtlas, 2016 


ASLA Chinatown Green Street Demonstration Project, Washington, D.C.

City of Greensburg Main Street Streetscape
, Greensburg, KS

Green Street, City of Edmonston, Maryland

Green Alleys, City of Chicago, Illinois

NE Siskiyou Green Street, Portland, OR
Kevin Robert Perry

Portland Mall Revitalization, TriMet and the City of Portland, OR
ZGF Architects, LLP

SW Montgomery Green Street: Connecting West Hills to the Willamette River, Portland, OR
Nevue Ngan Associates

The Creative Corridor: A Main Street Revitalization for Little Rock, Little Rock, AR
University of Arkansas Community Design Center





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