Sustainable Complete Streets
Communities across the country are realizing the ‘green’ potential of their streets. Making our transportation system more sustainable involves many policies and practices that minimize environmental impact and create streets that are safe for everyone, regardless of age, ability, or mode of transportation. Complete Streets are a natural complement to sustainability efforts, ensuring benefits for mobility, community, and the environment.
Many elements of street design, construction, and operation can work in favor of achieving both Complete Streets that work for all travelers and ‘green’ streets that serve environmental sustainability. Of particular concern are drainage and stormwater runoff issues too common in traditional streets. Optimal stormwater management looks beyond simply removing rainfall as quickly as possible, which risks negative environmental impacts associated with both stormwater quality and quantity, like polluted runoff, sedimentation, and bank erosion. Instead it focuses on efforts to retain and treat – or even eliminate – runoff at the source through cost-effective green infrastructure , improving water quality and complementing Complete Streets efforts.
Wide streets are problematic for mobility and ecology – they can be unpleasant or, worse, unsafe, for anyone traveling along or across via foot or bicycle and the large swaths of impervious pavement necessitate expensive drainage and treatment systems that can have harmful effects on water quality and quantity. Drainage facilities can affect pedestrians, bicyclists, and public transportation users in various ways as well. Poorly maintained systems create puddles that splash pedestrians and those waiting in bus shelters and that are hazards for bicyclists, hiding potential cracks that could spell rough spills.
When a Complete Streets policy is carefully followed, considering community context and needs, the issues of too-wide streets can be addressed while also increasing access for all travelers. Many communities are narrowing travel lanes, swapping one automobile lane for two bike lanes (a ‘road diet’), or taking other measures to provide safe space for bicyclists, pedestrians, and public transportation – without widening roads. In some cases, this can mean including only one sidewalk, as it did on residential 2nd Avenue in Seattle, Washington where a relatively low volume of pedestrians and slow vehicular speeds made this solution possible. Some cities are investing in pervious surfaces, such as pervious asphalt and concrete, pervious pacers, and reinforced gravel pacing, can be used on Complete Streets once it has been determined the surfaces will not compromise pedestrian and bicyclist access and safety. Furthermore, communities can look to maximize pavement albedo (reflectivity) to reduce the urban heat island effect, improve air quality, increase pavement durability, and improve nighttime illumination.
Landscaping elements that help curb stormwater runoff – bioswales, planters, rain gardens, and street trees – are mutually beneficial for mobility and ecology. Such green elements are increasingly found to be important deterrents of crashes and injuries, and contribute to a more comfortable and visually interesting environment for all users. When redesigning streets, project managers can include plants and trees (most likely requiring amended soils) to clean runoff and manage stormwater at the site. Traffic-calming elements like chicanes, islands, and curb extensions – all popular in creating Complete Streets – provide site opportunities for bioswales, street trees, and rain gardens.
Centrally located in Seattle, the Taylor 28 residential mixed-use project included a zero-discharge streetscape with each planting area serving as a rain garden. Curb extensions are home to some of these rain gardens, and also help to slow traffic, allowing bicyclists a safer ride. Numerous trees reduce the heat island effect and offset CO2, while widened sidewalks and increased pedestrian features make the street friendlier to those walking by. Such improvements complement the City’s own Complete Streets policy.
Of course, Complete Streets make their most basic contribution to green streets by providing space along the right-of-way for low-emission travel. In the United States, transportation is a significant source of greenhouse gas (GHG) emissions – in fact, it accounted for 28% of total U.S. GHG emissions in 2006. The largest source of transportation GHG emissions is personal cars and trucks. Complete Streets policies are an essential tool in providing transportation choices beyond the personal automobile. Walking and bicycling for the shortest trips (less than 1 mile), rather than taking a car, could reduce CO2 emissions – a major GHG – by 12 to 22 million tons per year in the U.S. Replace the car with walking and biking for longer trips (1–3 miles), and the CO2 savings come to 9 to 23 million tons annually. Add in the benefits of access to public transportation ridership – which is already cutting CO2 by 37 million metric tons every year – and the environmental benefits of Complete Streets are astounding.
Complete Streets, in conjunction with green infrastructure, is a tremendous opportunity to improve the livability of our communities, both now and for future generations.
[all citations are available in the downloadable files]
Managing Wet Weather with Green Infrastructure
U.S. Environmental Protection Agency
Street Design: Part 2 — Sustainable Streets
Public Roads, Volume 74, No. 5, Federal Highway Administration
Better Streets Policy & Plan
City and County of San Francisco, California
Right-of-Way Improvements Manual: Streetscape Design Guidelines – Green Streets
City of Seattle, Washington
Living Streets Manual
City of North St. Paul, Minnesota
Designing Our Future: Sustainable Landscapes
American Society of Landscape Architects
Sustainable Streets Online Seminar Series
University of California at Davis, Sustainable Transportation Center, 2008
Low Impact Development Resources
Low Impact Development Center
The Heat Island Group at the Lawrence Berkeley National Laboratory
Transportation’s Role in Climate Change
Transportation and Climate Change Clearing House, U.S. Department of Transportation
Moving Cooler: An Analysis of Transportation Strategies for Reducing Greenhouse Gas Emissions
Urban Land Institute, 2009
Active Transportation for America
Rails-to-Trails Conservancy, 2008
The Broader Connection between Public Transportation, Energy Conservation and Greenhouse Gas Reduction (.pdf)
ICF International, 2008
Green Streets: Dealing with Stormwater Runoff
Net Green News
Sustainable Design at High Point Redevelopment
City of Seattle
Green Street Program
City of Portland
Green Alley Handbook (.pdf)
City of Chicago