Streets have always been the workhorses of the cityscape. No matter the era, they serve as the indispensable lifelines that allow people to move and commerce to function.
But ideas about how — and by whom — streets are designed and the priorities that shape them can change from generation to generation. In the 1960s, as urban cores were decanting population to their suburbs, traffic engineers took the lead in redesigning city streets to be more like those of their car-oriented “competitors.”
Today, as many cities are scrambling to manage resurgent population growth and increasing density, urban streets are being overhauled in a radically different direction. Much of the change is a response to the sheer volume of people and vehicles. To move more people, “many cities are trying to redesign streets overbuilt for cars to be safer for walking and biking and improve transit speed and reliability,” said Aaron Villere of the National Association of City Transportation Officials (NACTO).
Growing cities are finding that streets must not only serve as the urban circulatory system, but the same right-of-way also must act as the kidneys and lungs of the municipal organism — clearing waste from storm water, improving air quality and providing space for residents to breathe. “With fast-growing places, each bit of green needs to be optimized for human benefit and ecological function,” said Dr. Kathleen Wolf, a researcher at the University of Washington who has spent years investigating the role of urban vegetation, in collaboration with the U.S. Forest Service. “And to the degree possible, each piece of right of way needs to be optimized for green.”
Some cities now are beginning to take steps to fuse several strains of fresh thinking that have emerged over the last decade or so. “Complete streets” policies — adopted by more than 1,200 cities — aim to convert streets designed primarily for car traffic to also provide protected space for people on foot, bicycle or getting to transit. More than 30 U.S. cities, ranging in size from Macon, Ga., to New York City, are pursuing Vision Zero goals, trying with a combination of street design, education and enforcement to bring traffic deaths to zero in coming years. To meet requirements for water quality and grapple with intensifying rainfalls under climate change, many cities are supplementing concrete pipe systems with “green stormwater infrastructure” (GSI) that uses vegetated areas to collect and filter water. And with a growing body of research showing that the “urban forest” provides ecological, economic and even public health benefits, cities such as Seattle have created aggressive programs to preserve and expand tree canopy coverage.
How do these threads weave together? “Trees and other plants clean the air, add economic value to real estate and commercial sales and they make places where people want to be,” said John Massengale, author with Victor Dover of Street Design: the Secret to Great Cities and Towns. “Perhaps most importantly, they slow cars down, which is critical to achieving Vision Zero. If we slow cars down to 20 mph or less, almost nobody will be killed whether pedestrian, cyclist or driver.”
The notion that street trees promote safety is heresy to a previous generation of traffic engineers, who worked to eliminate sturdy trunks that could be a hazard to motorists should they swerve off the road. But it’s true, said Wolf. Her evaluation of years of research shows that, while trees might be a hazard in rural areas, it is just the opposite in cities, where speeds are slower and sharp curves rare. “It’s not like trees jump into the lane,” she noted. Rather, research shows the presence of roadside vegetation creates a calming effect that slows speeds, and thereby reduces both the likelihood and damage from a collision.
Green streets in “ultra-urban” areas: Denver steps out
But where to find space for more of that vegetation? It turns out that some of the same techniques that can be used to calm traffic and create safe zones for people on foot or bicycle also offer opportunities to introduce more soothing vegetation and ecological functions. Many of those approaches, as well as case studies, are covered in a guide book from NACTO released in mid-2017.
Among the cities leading the way in putting all these elements together is Denver. The city began to rethink its approach to streets as long ago as a 2008 with an initiative that came to be known as Living Streets, said Crissy Fanganello, the city’s director of transportation and mobility. “Working with our advocacy community we began to think about streets as places and how to design for all users.” The city adopted a complete streets policy and began installing protected bike lanes and retrofitting larger streets to reduce speeding and provide refuges for people on foot.
But then came a post-recession development boom, with growing numbers of people walking and biking in the city’s denser neighborhoods. Even as the intensity of development increased, the city also was under the gun to stop dumping polluted runoff from “impervious surfaces” into the South Platte River. Although agencies responsible for transportation, utilities and trees and open space tend to work in silos with their own funding streams, Denver officials realized that would no longer be good enough. Over the last couple of years, experts from the various agencies formed a new joint initiative and with the city’s engineers developed a ground-breaking guide to retrofitting streets in “ultra-urban” areas.
“The pollution removal value of green infrastructure is well established,” Fanganello said. “We want to help prove nationally that it also can have a traffic calming and safety benefit on our streets.”
A series of path-setting new projects is now in play. As a showcase for what is possible, contractors in early 2019 will transform 3.5 acres at the intersection of 21st Street at Broadway, between Champa and Stout Streets, from an asphalted moonscape hazardous to people on foot and bike to a green plaza with protected bicycle and pedestrian ways. “Tree trenches” will shade the area while sucking up runoff and provide a calming green frame for what had been a six-lane speedway. A “green alley” of plants will separate the bike and pedestrian ways. A “water quality planter” will transform pavement into a lush garden spot worthy of lingering. “The project started as a traffic signal and bike lane, but we worked together to make it something much more,” said Brian Wethington, water quality project manager at Denver Public Works.
In the city’s River North arts district, known as RiNo, work already is under way along 15 blocks of Brighton Boulevard to convert a barren stretch of hardscape into an inviting place to walk, bike or wait for the bus. A first phase of the project is catching half the stormwater runoff, while a second will capture every drop. Along the way, the boulevard will be lined with varying “amenity zones” that can include tree trenches, landscaped planting strips, benches for resting and art to contemplate. As with 21st Street, the trees provide shade for those on foot, while plantings will separate cars from bikes and bikes from pedestrians.
How to fund innovative street design? Seattle looks for a breakthrough
Over in the Pacific time zone, Seattle has been an early adopter of ideas around green and complete streets. It was the first big city to adopt a complete streets ordinance, calling for all significant street maintenance and construction projects to improve safety for people on foot and bike. In 2015, it became one of the first American cities to adopt Vision Zero. In the mid- 2000s Seattle also was a pioneer in redesigning streets both for managing stormwater with nature and safer walking, remaking a 12-block grid with new sidewalks, landscaping to “enhance the pedestrian experience in the neighborhood,” all while benefiting wildlife habitat and improving water quality.
The challenge for Seattle has not been developing and demonstrating integrated thinking about streets, but overcoming the funding silos that make innovative projects so difficult. But with a nation-leading population influx and a forest of cranes looming overhead, Seattle has no choice but to overcome that obstacle if it hopes to keep people moving while meeting goals such as maintaining 30 percent tree canopy, said City Councilmember Rob Johnson.
“I see green infrastructure and complete streets as inextricably related,” said Johnson, who recently and successfully championed significant funding for green infrastructure in the street rights-of-way. “But it means changing longstanding habits of thinking about urban infrastructure, how we build and how we fund it.”
While the city always has more needs than money, the challenge has been more about agencies syncing up available dollars with each other’s plans. The city’s water utility, for example, has substantial funds dedicated to green infrastructure as part of its commitment in a 2015 consent decree to reduce untreated sewage and stormwater flowing into waterways. But that money can only be used in the limited areas where soils permit adequate drainage, said Mami Hara, general manager/CEO of Seattle Public Utilities (SPU).
“Regulatory compliance has been our driver,” Hara said. “Flood prevention and other uses of green infrastructure are not part of that equation.” That’s why Hara, who was recruited from GSI pioneer Philadelphia, to expand its use in Seattle, was thrilled when City Council approved six years’ worth of funding to go “beyond compliance.” “We now have two buckets of funds: one for compliance and the other that can address localized flooding, ameliorating impacts of densification to manage stormwater and surface pollution.”
That frees the agency to partner more with the Seattle Department of Transportation (SDOT), which is undergoing an aggressive effort — funded in part by the city’s largest-ever transportation levy — to redesign and add sidewalks and bike ways on a multitude of streets in the face of rapidly escalating demand. The two agencies have tried to establish consistent lines of communication so that they partner on projects, regardless of who initiates them. So, for example, when SDOT has a project under its Safe Routes to School funding umbrella, planners can incorporate green features in the curb bulbs used to narrow street crossings around schools, or add swales and street trees, said Brian Dougherty, who oversees the program at SDOT. Likewise, SDOT works to put the “green” into neighborhood greenways, corridors that are designed to be safe for families and all ages to walk or bike. “We always try to add vegetation where we can, whether or not it serves a specific stormwater management function,” Dougherty said.
Green and complete streets provide public health and safety benefits to low-income neighborhoods.
The next big hurdle: Getting legal authority and policy direction to do joint projects with private developers and other entities. “We are not just looking at parsing out public money for projects here and there,” said Hara. “We have to find ways to partner and leverage private investment as well.”
Working equity into the equation
When city governments scan the landscape for areas with dangerous conditions for pedestrians, a propensity to flood or a lack of tree canopy and soothing vegetation, more often as not they find themselves in low-income neighborhoods of color, said Denver’s Fanganello.
“Equity is important to talk about,” she said. Here again, funding streams and regulatory habits can be an impediment. “Typically, when we have done landscape improvements along a roadway, the city would put in capital, but we would need an entity like a local improvement district to maintain it. The areas of the city that can do that usually are more affluent. This can mean that the very areas where more people are hurt or killed on the street are not seeing the amenities and benefits.” Denver has more recently established a policy of maintaining green and complete streets in low-income areas, she said.
Seattle, too, is working to apply an equity lens in choosing projects. “Part of going ‘beyond compliance’ for us is to try to prioritize the vulnerable neighborhoods that have flooding problems and need green space,” said Shanti Colwell, GSI program manager at SPU.
A growing body of research shows green and complete streets provide particular public health and safety benefits to low-income neighborhoods and communities of color, though the bonuses are not limited to that population, said Wolf. “Going to parks is great, but not as important as the connectivity through neighborhoods,” she said. “That’s why green streets are so important: They are good for children getting to school, people walking to work or transit, or to do errands. These environments encourage and even motivate people to go out and be active, and they reduce stress. They’re critical to a healthy, thriving city.”David A. Goldberg is a nationally recognized journalist and founding communications director of two national nonprofits, Smart Growth America and Transportation for America. In 2002, Mr. Goldberg was awarded a Loeb Fellowship at Harvard University, where he studied urban policy.